The following are simply a selection of sites of speleological
interest, to give a flavour of the north Wales caving area.
Although most of these sites are only minor when compared with those of other areas, some of them could repay organised excavation work.


Alyn Gorge Swallows

The River Alyn has been known for centuries to disappear in river bed 'swallows' downstream of Loggerheads. In the past this caused flooding into the lead mines below. As a result, in the 1930s Halkyn District United Mines (HDUM) carried out a thorough programme of work aimed at identifying and sealing the main areas of leakage along the river bed. Despite dozens of individual swallows being cleared down to depths of over 20 feet, the major hydrological conduit was not found that could have been sealed to prevent flooding in the mines. In the long-term however, their work had little effect, and today the river appears to run dry for long periods each year.
HDUM produced an unpublished report on this work which details the main areas of leakage and how each area was treated. A shortened version of the report has been digitised and is available as a PDF download at very bottom of page.

In 2018, a major swallow opened up in the river bed at Devil's Gorge and one of the nearby Leet caves collapsed internally, revealing a natural shaft in the floor. At the bottom of this shaft is a muddy chamber. The cave has since been gated by Natural Resources Wales and the large new swallow in the riverbed is being regularly monitored. Close to this new swallow, a collapse of debris lying against the cliff-face revealed a previously unknown cave chamber. This has been fenced off by Loggerheads Country Park and cavers are closely monitoing the situation. See the entry under Leet Caves for more information.


Brasgyll Rising SJ007714 River Elwy

A permanent spring, the source of which is presumably Brasgyll Gorge (see Brasgyll Caves). Not known if cavers have dug here in the past. It looks as though a few hours are needed to clear the entrance of boulders in the hope that open passage can be found above water level. Only 300m from this rising to Jock's Pot in Brasgyll Gorge.

From Brasgyll Caves walk downstream almost to the River Elwy, but climb out of the stream bed where a new (2013) track crosses above. Turn right onto the track and through the gate. The rising lies about 20 metres from the gate, water from the resurgence crossing the path.

In the 1970s, a second rising was seen by the writer to be active active in flood conditions, but landscaping work in 2012/13 has buried it, and no visible trace remains.

It was situated west of the Brasgyll stream, a few metres south of the bank of the Elwy perhaps 50 metres or so upstream of the Brasgyll stream, and close to an old timber fishing hut (which also no longer exists).


Caerwys Sink SJ12187401 Caerwys

A small winter stream runs south terminating at a large grass-lined depression. No solid rock visible and not inspiring, but this is the only known active sink that's likely to supply St. Michael's Well to the south (height difference: about 50m).

Take the back lane (west of the village) leaving Caerwys in a north-westerly direction. After 0.7 of a mile is a cross-roads (Barlows Caravan Site is just off to the left here). Continue north-west over the cross-roads for a further 200m looking for an overgrown path on the right leading to a gate. The sink is in the field over the gate.


Cefn-y-gist Shakeholes SJ232488 World’s End

A line of shakeholes formed at the base of the limestone beds. One or two take insignificant amounts of water. More water sinks at the most southerly of these shakeholes (Ogof Cefn-y-gist 1: See page 7) which once found its way to Ffynnon Wen (see entry below), the old resurgence at Minera, before mining lowered the local water table. The line of shakeholes are arguably one of the most promising digging sites in the area. Three shakeholes have been dug in the past, revealing stream passages about 4m in width. Sadly the thinly-bedded ceilings are unable to support such wide passages and large sections have collapsed. Two of the caves discovered have been re-sealed due to the degree of instability. A possibility would be to excavate others of the group in the hope of finding a narrower, and therefore more self-supporting passage.

Dye testing has shown that water sinking at Cefn-y-Gist now re-appears in Ogof Llyn Parc (NWCC newsletter No 285, 2003)

All shakeholes can be found by walking north from Ogof Cefn-y-gist .

View looking south towards World's End. The road is off the picture to the left

Shakeholes marked 1-18: Ogof Cefn-y-Gist 1 being No 18


Dinorben Farm Sink SH96807467 St. George, Abergele

A shakehole around which a C-road bends. A stream sinks about 40 metres before reaching the main shakehole by the road, but in 1974 the stream flowed into the shakehole. In 1983 a dig reached a depth of 5m by shoring against one wall of solid rock. At that depth a short rift was found which became too narrow and an impenetrable slot was seen in the floor. The dig might have been more successful if driven deeper at the same location.

Water sinking here is presumed to have been the source for St. George Cave, which was lost to quarrying and was ¾ of a mile to the north with a height difference of 65m (see page: 20: Lost & Non-Caves)

Access: Seek permission from the nearby Dinorben Farm.

Warning: Work here involves digging down through rounded stones and boulders and therefore requires substantial scaffolded shoring (rounded boulders being one of the most unstable mediums to dig through)

Steve Burzio at the dig in 1983


Dulas Resurgence SH9086277712 +/-24ft Llandulas

A promising rising on the bank of the River Dulas. Issues an impressive flow when seen in flood conditions. Some work was done by the writer and others here in 1974 and 1980, when a short blind mine level was entered at the head of the cutting. This was driven directly above the point at which the natural passage must lie. Inside the level the water fluctuates, being in communication, via a small hole in the floor of the level, with the spring below (see diagram below). The hill above the resurgence rises by over 170m, although there are no known sinks. The writer was told by a caver many years ago that, looking for bats he explored a blind mine level in the hillside to the south after a period of heavy rain, and at the end of the passage he could hear the sound of flowing water coming from the rock face ahead. The location of the mine passage was pointed at as being very approximately SH906770, and about half way up the hillside.

An old quarry lies about 500 metres to the west on the hill above the resurgence. A dye-test was carried out in the quarry by the Environment Agency, who also took 200 samples at the resurgence between 1996 and 2004. The dye test was carried out before the quarry floor was fitted with a polyethylene membrane, which was then covered in a metre of clay. The EA discharged a tanker-full of water containing fluorescein dye into a groundwater sink in the quarry at SH9035677418. Dye re-appeared at the resurgence after 38 hours (Source: Personal communication, Environment Agency 2010).

The cutting leading to the resurgence requires excavation to lower the depth by perhaps 2 metres in the hope of exposing the assumed cave entrance. The work in 1974 began this task by shifting some 10 tons of clay and rock. A JCB would make easy work of the task.

At Llandulas, take the C-road due south from the old Llandulas - Abergele road. After less than half a mile, the road crosses the River Dulas. Park next to the bridge and take the stile on the right on the far side of the bridge. Walk downstream for about 50 metres and the spring is on your left.

Presumed cross-section of Dulas resurgence

Lowering the cutting in 1978

Environment Agency V-notch monitoring weir in 2009 (possibly now defunct)


Esclusham Mountain Shakeholes Minera - Llangollen

A narrow band of limestone extends from Minera in the north, through World’s End, to Llangollen in the south, the outcropping limestone being up to half a mile in width. This area contains around two hundred shakeholes. Most are closed and grass-covered at their bases, but several are open and a few take small trickles of water. The whole area is wild moorland carpeted with rough heather which makes walking difficult. The aquifer within this limestone area (World's End to Llangollen) is fed chiefly by percolation and resurges at the permanant Oerog Spring at Trevor. Two other flood resurgences lie nearby, one of which can be entered (Trevor Flood Resurgence Cave), although the passage descends below the water table and becomes too tight.

Water sinking just to the south of World's End at Ogof Noeth is thought to resurge at World's End Cave. The nearby Kiln Cave at World's End acts as a flood resurgence only.

As the shakeholes can be difficult to find, a survey was carried out by the writer in 2009/10 to identify those with open holes at their bases. Most shakeholes were flagged using Google Earth and, by using a free computer programme (Tyre), these were transferred to a GPS (ETrex legend HCx). Using this method it was possible to plot GPS routes to the flagged shakeholes. This method was very successful in plotting walking routes to include areas of cleared ground that avoided much of the deep heather.

Almost 200 shakeholes were examined, of which 26 were found to have open holes at their bases, although not all are promising. At the time of the survey, none were examined internally, although most may have been examined in the past. The table below may help future explorers at least to find some of the more promising holes on the mountain.


Shakehole A002

Shakehole E014


Ffynnon Asaph SJ07527894 Dyserth

Also known as Ffynnon Asa

A powerful spring with a flow of 3 million gallons per day. The catchment area contains no known caves. The water rises from a gently sloping field and is contained within a locked water authority building. Sinks within the catchment area include Brynglas Sink and Hendre Fawr Sinks........

Brynglas Sink SJ08777731 Trelawnyd

A small winter stream sinks in a vertical-walled hole in clay. In 1974 the floor fell away leaving a 9m deep hole but no solid rock was visible. Not known to pool up.

Not a particularly promising site but this is one of the few swallets associated with the Ffynnon Asaph system.

Close to the lane on the west side, in the north-east corner of the field.

Hendre Fawr Sinks SJ097770 Trelawnyd

In wet weather two small streams converge and sink at several locations along the stream bed. Most swallows are upstream of Hendre Fawr Farm. Upstream of the road bridge several further sinks can be found at an old small stone quarry on the south bank (at SJ099769). Other swallows lie in the stream-bed just downstream of the bridge, where solid rock outcrops almost at surface. A dig in 1974 was carried out by the writer, opposite the farm on the north bank, and reached a depth of 3m in loose and fissured limestone on the south side of the dig. It was however abandoned as it required serious scaffolding work at a time when most caving activity was centred on the Alyn Gorge following the discovery of OHA in 1973.

The overflow from Ffynnon Asaph in 1973 before the site was fenced off

The spring rises in a deep pool beside the stone building




Ffynnon Ddyfnog SJ07966334 Llanrhaedr, nr Denbigh

An impressive resurgence in flood conditions, which gives the overall impression of once being a wide, but now collapsed, bedding-plane. Water rises from several locations all within a few metres. Difficult to know where to excavate but promising potential.

The spring issues from the head of a blind valley near Llanrhaedr church. The height difference from the main active sink of Ogof Rhewl (page 7) to Ffynnon Ddyfnog is 100 metres, and the two locations are 1 mile apart, hence an interesting cave system awaits discovery.

An ancient curative bath has been built in front of the spring where local clergy performed 'miracles': They knew that Ogof Rhewl and Ty Mawr Reservoir Sink acted as feeders, so introduced red ochre into the sinking waters. After a specific time later, bathers were then introduced into the 'holy bath' and when the water turned to 'blood or wine', all were allegedly cured. Described in early literature as “A mighty spring much frequented for the cure of scabs and itch, and some said it cured the pox”.

(Source: Francis Jones: The Holy Wells of Wales).

For an area plan showing the sinks, resurgence and boundary of the carboniferous limestone, see Ogof Rhewl .

A little more on this spring, and a better photo of the bathing pool, can be seen at:

Travelling from Ruthin towards Denbigh, pass through Pentre Llanrhaeadr then turn off left into the village of Llanrhaedr. 50m past the church turn left taking the Prion road. A driveway 200m up on the left enters the vicarage. Just 20 paces before the vicarage entrance is a narrow opening in a high wall. Take this and scramble down following the noise of the water.

Ffynnon Ddyfnog bath and spring in dry weather in 2015

One spring issues just in front of the blue-jacketted figure. The other issues via a flooded hole and pipe at the top of the cascade on the right

View of the bath from the overflow


Ffynnon Leinw SJ18316773 Hendre

An old well that used to 'ebb and flow' until mining lowered the local water table. A 'curative' bath has been built directly over a natural spring. The bath was cleaned out by historians in the 1970s when the cave passage supplying the bath could clearly be seen. When checked out during a dry summer this passage was flooded, descending and appeared too tight. Prior to the lowering of the water table, the spring issued from the Caleb Bell cross-course (a major north-south fault), upon which the spring lies. The cross-course regularly caused flooding in nearby North Hendre Mine.

Photos of the well and the small passage that supplied the well can be seen at the bottom of the page at this link:

Driving towards Denbigh from Hendre, pass the Royal Oak on the left. About 400 metres beyond, the well is on the left about 10 metres from the road. Just past the well, woods on the left give way to open fields.


Ffynnon Wen SJ261518 (approx) Gwynfryn

This is now abandoned as a result of lowered water tables due to mining. Pre-mining, Ffynnon Wen was the main resurgence for Esclusham Mountain. Underground near this point, the waters from two caves once converged before issuing at Ffynnon Wen namely: Ogof Llyn Du and Grand Turk Passage. Ogof Llyn Du supplied water from caves to the west, namely, Ogof Dydd Byraf and Ogof Llyn Parc, whereas Grand Turk Passage supplied water from the rest of Esclusham Mountain, from a cave system that remains to be discovered. One of the furthest sinks to feed this system is Ogof Cefn-y-gist almost 2.5 miles to the south-west (see also Cefn-y-gist Shakeholes and Reid's Shaft Caves).


Froncysyllte Risings SJ27624127 Froncysyllte, nr Llangollen

An interesting area that might repay a little work. Four small springs lie along the limestone boundary, all lying between the canal and the River Dee. They drain an isolated block of limestone that rises to the south some 230m above the springs, much of the area having been quarried. Although only one spring appears to have any potential, the four are described in Ebbs’ diary for December 30th 1990 “under normal flood conditions”:
Spring A (SJ275414): Usually constant, but landowner said it dried out for a week last year. Lying in a gently sloping field, it’s been constructed as a well about 20 feet from a limestone outcrop. A further trickle issues from boulders about 5m to the west.
Spring B (SJ276410): Mid-way between the farm and Spring C in bank of stream behind V-notch weir. An uninspiring trickle.
Spring C (SJ27654130) at 65m AOD: An interesting site where bedock is visible. A waterboard V-notch weir creates a 4ft wide pool, water issuing from pebbles below the surface. The surrounding earth and sods need to be removed and the water level lowered, to check for horizontal passage development.
Spring D (SJ28054105) at 80m AOD: A small trickle runs from a flooded hole partially obscured by tree roots. Bedrock not visible but may lie just a few feet down. The water level was lowered by trenching without finding any horizontal development, water rising from lower down. Pebbles along the streambed are stained white, presumably calcited.

Access: Seek permission at the house in whose garden the spring lies.


Gwter Siani Sinks SJ24944982 Esclusham Mountain

A stream flowing west sinks in a small blind valley. There are several places where water here runs underground and several blocked holes formed by subsidence. In flood conditions however, this area has been seen to pool up and form a small lake. One hole was excavated in the 1980s but was abandoned when no solid rock was found, just large loose boulders. No draughts have been identified. This site and Cefn-y-gist Shakeholes are the two main inlets for the undiscovered Esclusham Mountain master cave.

Park at SJ251500 then walk south-east for about 80 metres to the blind valley.


Lodge Farm Swallow SJ03866685 Denbigh

A swallet which awaits excavation. Water sinking here is likely to resurge at Ogof Ewenol 2.4 miles to the north-west, although no dye testing appears to have been carried out to confirm this.

The swallet lies at 130m AOD and Ogof Ewenol at 40m, hence a height difference of 90 metres.

Access: Consent is required. Call at Bryn Nefydd Farm on the Denbigh - Henllan Road, immediately before turning off down the lane.

Drive out of Denbigh on the Henllan road. After passing Coppy Farm and the cliffs on the right, take the easily missable left turn immediately after a solitary house. After about 100m take the only track/footpath on the left. The sink is on the right close to the track after about 50 or 60 metres and is now surrounded by 2m high fencing.

The current point at which water sinks amongst boulders within the collapse area (2012)


Oerog Spring SJ26174205 Trevor, nr. Llangollen

The main rising for Ruabon Mountain with a flow of about 720,000 gallons per day. The point of issue is housed within a water authority building. Water rises up through gravels and is therefore of little caving interest. At times of heavy rain, Trevor Flood Resurgence Cave becomes active and is presumably the overflow resurgence for Oerog Spring.


Oxford Pot SJ18346562 Cilcain

A sinkhole which enlarged considerably as a result of floods in 1976. The farmer responded by inserting a Morris Oxford into the hole. GCC cleared a route about 3m deep and 3m horizontally ending at impenetrable fissures. May need digging deeper. Pre-glacially, the River Alyn flowed north over this location (after Embleton 1957) and the assumed cave below may represent an early swallet cave.

To find the hole, just follow the only stream at this NGR. The stream is piped under the road and into the sink about 20 metres away, close to the track which runs down to Hesp Alyn Farm.


Park Farm Swallets Approx: SJ245511 Esclusham Mountain

An area to the west of Aber Sychnant having several interesting shakeholes.

One has been excavated for 30m following a low passage (see under Park Farm Cave or PF2 below).

Several other swallets and open fissures can be found in the Aber Sychnant gorge and those that take water have a h ydrological connection with the nearby Ogof Llyn Parc to the south-east.

The area was revisited in August 2013 when the following GPS locations were obtained for the most interesting sites.....

PF1 SJ 24633 51387 +/-10ft (Shakehole)

PF2 SJ 24577 51267 +/-7ft (Park Farm Cave)

PF3 SJ 24546 51195 +/-10ft (Shakehole)

PF4 SJ 24563 51116 +/-12ft (Shakehole)

PF5 SJ 24592 51132 +/-7ft (Shakehole)

PF6 SJ 24572 51056 +/-7ft (Swallet)

PF1 shakehole

PF1 shakehole. Takes a trickle only during wet weather

For PF2, see under Park Farm Cave

PF3 shakehole

PF4 shakehole

PF4 (upper left) and looking towards PF5 (right)

PF5 swallet in 1978. The stream now sinks at a swallet 100m upstream (see PF6 below)

PF5 shakehole in 2013

PF5 shakehole . Showing the point of sinking in 1978 (see photo above)

PF6 Swallet looking towards PF5. Swallet indicated by lighter shaded oval.

PF6 swallet. This takes a permanent stream which can be heard falling below surface.
No evidence that excavation has taken place in the past

Aber Sychnant gorge looking north (downstream)


Rhydlydan Rising SJ13567350 Caerwys

This site is no longer open as it has been filled and no trace now exists (2018).

A vertical rift 1m wide x 3m long excavated by the writer and others in the 1970s to a depth of 5m to a flooded sump with fluctuating water levels. At this depth the east wall veers away to form a roof with one or two stalactites. The rift resurges in extreme floods and the land-owner claimed that he once heard roaring at his farmhouse (half a mile away), caused by waters issuing from the rift after exceptionally severe flooding. Unfortunately the limestone bedding dip to the east, hence any passage found is likely to lie below the water table. The site may possibly be of interest to cave divers, but the rift would need a drought followed by much work to remove remaining infill.

From the road, walk downstream on the east bank for about 30 or 40 metres The entrance is a little above stream level off to the left a few metres past the ruins of an old cottage.

It's also worth mentioning that there's a permanent spring (Ffynnon Deg) 400m further down the valley (SJ13357328) and 500m further again there's a slot in a small outcrop where the sound of a small underground stream (perhaps a trickle) can be heard (SJ13377280).


Seven Springs SJ1907059744 +/-12ft Llanferres

Several springs issue at or near a small shallow pool besides a footpath stile. An old mine level was commenced close to the spot but nothing is known of its history. The level was excavated by cavers for a few metres to where it's questionable that it ever went further. The source of the water is uncertain although a couple of shakeholes once existed in the valley close to Burley Hill Quarry, before being filled by the quarry company. In flood conditions water rises up from the footpath about 200m to the south-east of the springs at the position of a north-south cross-course (fault).


St. Michael’s Well SJ12287292 Caerwys

A tempting resurgence which issues from a flooded, low, descending passage. Cave divers describe the passage as being partially blocked by boulders and requiring underwater digging. Although being the resurgence for a fairly large catchment area, the only active sink known is the uninspiring Caerwys Sink (see also Caerwys Caves higher up the valley).

Warning for cave divers: A small sewage plant overflow empties into the dry valley about 50m north of the well.

Although not far down-valley from Caerwys Caves, access to the well is almost impossible from the caves . The well is better reached by taking the bridleway from Caerwys golf course to a corner at SJ12307251. Turn right by a stone post and follow a rough path through woodland just beyond the golf course fence. At Coed Farm (just visible above) , turn downhill through the trees to meet on obvious path (a few metres) below. (This 'path' is a Forestry vehicle track leading to a junction within a few metres, one route leading down to the stream). Follow this down to river level. Walk upstream keeping to the river bank passing two mined chambers at SJ12237275 to the well beyond.

(Access information: Dave Merchant)

NB Not easily accessible in late Spring or Summer, due to brambles at stream level and footpath undergrowth (June 2018)


St. Winifride’s Well SJ18537627 Holywell

A holy well still used for curative and remunerative purposes.

This was the strongest resurgence in north Wales. The point of issue is enclosed within a masonry shrine and a small charge is levied to enter the grounds. It was the resurgence for the Halkyn Mountain cave system , having a pre-mining flow of nearly 6 million gallons per day (over 4000 gallons per minute).

When the Milwr Tunnel was being driven 2.7 miles to the south-east, it intersected a cave system in 1917 causing the well to dry up entirely. Water is now piped directly from the nearby Holywell Boat Level. The well is "219.2 feet" (66.8m) AOD and its waters originally rose through fissures in chert at the point where a major fault (the Caleb-Bell cross-course) intersects the Old Holway vein.

St. Winifride's Well is the resurgence for the catchment area of south-east Halkyn Mountain, from Holywell to Rhosesmor (lying east of the impervious Pant-y-Nef cross-course). The western catchment area (west of Pant-y-Nef cross-course) resurges at Ffynnon Asaph near Dyserth. There are also much smaller resurgences, such as St. Michael's Well, Caerwys which play a part in draining Halkyn Mountain. St. Michael's drains a small area between Caerwys and the A55 expressway to the north.

The legend and its religious significance can be found at

Analysis of the water in 1873 prior to draining by mining (Source: Strahan 1890) shows:

Temperature: 11 degrees C (52 degrees F)

Specific gravity: 1.0015

Carbonate of lime: 13.685 grains per imperial gallon

Carbonate of magnesia: 2.688 grains per imperial gallon

Sulphate of lime: 5.202 grains per imperial gallon

Chloride of sodium: 0.851 grains per imperial gallon

Chloride of calcium: 3.094 grains per imperial gallon

Carbonate of soda: 1.432 grains per imperial gallon

Silicic acid: 2.737 grains per imperial gallon

Further analysis of 1874:

Total solid impurity: 36.44 parts per 100,000

Organic carbon: 0.045 parts per 100,000

Organic nitrogen: 0.009 parts per 100,000

Chlorine: 6.30 parts per 100,000


Ty Graig Swallets SJ201504 Llandegla

Also known as Fourteen Swallets

In the 1980s there were 14 shakeholes or swallets formed along the Bryneglwys Fault. Numbers 1 to 13 extend south-west from Ty Graig house. Number 14 lay in the middle of a field about 100 metres north-east of Ty Graig (SJ20315070). It took a small winter stream which sank in fissures in solid rock, but the water that supplied it has now been piped to the hole and the pipe buried, obscuring the swallet completely. Looking at the Google Earth image below, it appears that some shakeholes may have been lost by filling (up-to-date information required).

Only one or two of the larger shakeholes seem to be worth digging, one being 5m deep with a 2m pot at its base. They look easy work through loose boulders, but the distance to either of the two risings is only a few hundred metres at most (Main rising SJ20045061).

In 1965 flourescein was added to the small stream entering one of the furthest swallets from the farm (No 1 or 2?). After three days activated charcoal from "the nearby resurgence" was tested and proved positive under UV light. This followed an earlier negative dye-test which relied only upon visible discolouration at the resurgence after just 35 minutes (Source: Ellis, B.M. [1966] Some Caves of North Wales, in Shepton Mallet Caving Club Journal No 1 June 1966).

Access: Seek permission at Trefydd Bychan Farm next to Ty Graig.

NB The fourteen swallets numbered are those that existed in the 1980s.

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An attempt at sealing natural water-holes or ‘swallows’ in the River Alyn (1139k) HDUM (1938)/Cris Ebbs (2020)