Porth-yr-Ogof, Porth yr Ogof - Main Entrance, White Horse Cave, Cwm Porth Cave, Porth Ocho cavern

NGR: SN 92820 12415
229 m.asl

Powys , Northern Outcrop - Central (Penwyllt to Penderyn)
map using leaflet map:
Sink Cave
Access The cave is a well known tourist spot and is marked on OS maps. From Ystradfellte, take the road towards Pont Nedd Fechan. After less than 800 metres, a single track road leads off on the left. The road descends to where a large car park is situated above the cave.
Description A large entrance, which takes the complete flow of the Mellte can be followed for 230 metres, but care is needed with the downstream sump as the current is strong. An extensive dry series leads off a chamber to the right of the entrance. The cave is visited daily by Adventure Groups. There are no less than 15 entrances / exits to the cave. NB. The resurgence is extremely dangerous and 10 people have drowned in the resurgence pool as of 2002.
History Wessex CC 1937
GCR: 555
T.A.J.Braithwaite (1936)
Caves and Caving 1, (3), 93-98, 1938
CRG 1959
UBSS 1968
Lithophylach Britannici Ichnographia (1699; 1970) Lhwyd, E., Letter to John Ray (De Fossilium Marinorum E Foliorum Mineralium Origine)
The Scenery, antiquities and Biography of South Wales, Makin, B., 2ed, 1807 pp.212-213 "...the Melta river rolls in a sinuous course, wearing its channel through the rock, deeply perforated into fathomless pools, whence it issues into daylight, after a subterraneous passage of at least eight hundred yards. There is a practicable passage through it; but the attempt is imprudent. It is necessary to carry candles...In one instance a life was lost; though my guide had been through several times, and was ready to undertake it with any visitor. We penetrated about an hundred yards, as far as any glimmering of daylight from the mouth directed us: and this specimen of Stygian horror was amply sufficient to satisfy all rational curiosity..."
Cambrian Travellers Guide, Nicholson, G., 3ed,p.5041813;;1840, "...Porth-yr-ogof (the mouth of the cave)...This portal resembles the long and heavy stone mantelpieces over the fireplaces of our ancient halls. On entering this cavern the rocks are of unequal height at one step low enough to permit a tall man to without stooping and at the next a child of 10 years old must creep all fours. On the l. a nearly perfect dome is discovered from the roof which are suspended stalactites and other calcareous concretions in abundance which make a brilliant appearance when lights are introduced. On the same side of the river, a little lower and further in the cave, the river Mellte is heard rippling among the stones and soon after it leaps into a tremendous deep black pool in the centre of the cavern. The whole of the scene is horridly grand. At the lower end of this acherontic gulf, in a black rock is a vein of calcareous spar, supposed to resemble a child standing upon a pedestal, whence it is called Llynn-y-baban. Here the river is again lost for about 120 yards, after which, in floods, it bursts out below, with great fury. On the r. is another branch of the cavern supposed to extend many miles in length where persons are said to lost their way..."
A Topographical Dictionary of Wales, Lewis,S.,Ystrad-Velltey, 1833;1844;1849, "Porth yr Ogov, or "the mouth of the cave." This remarkable cavern is entered by a horizontal aperture, twenty feet high and about fifteen yards wide, leading into a spacious apartment with a vaulted roof, from which hang stalactites and other calcareous concretions, which, on the introduction of lights, exhibit brilliant and splendid reflections, of numberless hue...In the month of June 1842, when the Melltè was unusually low, the author of the admirable "Book of South Wales" succeeded in penetrating more than 500 yards through Porth yr Ogov, walking occasionally by the side of the stream, as far as the White Cave, a point which the guide had only succeeded in reaching once before. Here, the light was seen gleaming through an aperture at some distance; the water was found to be deeper, and it appeared to be impossible to proceed further. The fatigue to the visiter is great, as it is necessary to assume a stooping posture for the greater part of the cavern."
Guide to the Beauties of Glynneath (London, 1835), Young, W. "Porth-yr-ogof, or cave; this is a remarkable object; for although openings or caves in the limestone rock may be said to abound in the vicinity, there is not another in the valley of so large dimensions; you have light enough from the entrance to go in a considerable distance; if provided with candles, you may venture in two or three hundred yards, but there is nothing very remarkable to be seen."
Wanderings in South Wales (London, 1836), Roscoe, T. p.256
Trans.Cardiff Naturalists Society, 3, 1872
Trans.Cardiff Naturalists Society, 20, (2), 128, 1888
Trans.Cardiff Naturalists Society, 21, (1), 40-41, 1889
The Geology of the South Wales Coalfield, Part V, A.Strahan, T.C. Cantrill, 1904, p.30
In the March and Borderland of Wales, A.G.Bradley, 1906, pp.376-378 [a visit in 1905]
Cullingford,C.H.D. (1951), Exploring Caves, p.72-73
SWCC Newsletter 19, 7-8, 1957
SWCC Newsletter 10, 1954. Flooding
SWCC Newsletter 20, 1, 1957 R.Smith
SWCC Newsletter 45, 20, 1963 J.Hartwell
River Scenery at the Head of the Vale of Neath (Nat.Mus.Wales, 1ed, 1932) North, F.J.
Caves and Caving 1, (3), 93-98, 1938.
British Caver 4, 13-19, 1939. Extract from Glamorgan, 1938
British Caver 6, 44-53, 1940
Yorkshire Ramblers Club Journal 7, (23), pp.52-61, 1938. Early description
HCC Newsletter 2, 2-3, 1951
HCC Newsletter 3, 6, 1952
Caves in Wales and the Marches (Dalesman), Jenkins, D.W. & Williams, A.M., 1st Ed.1963
Michael Faraday in Wales, Dafydd Tomos (ed), [1973], pp.49-50: 21 July 1819 "...Porth Ocho cavern...Ascending to a farmhouse above, the guide lighted his roll of old sacking and we tramped to the other end of the cavern about 700 yards off. On arriving at the front of the cavern we came on to a causeway of Marble rocks leading up to a broad wide arch of the same material, beneath which a river led by a rocky channel disappeared in perpetual gloom. We entered with the stream upon its pebbled and bouldered bank and groped our way in diminishing daylight until the roar of surrounding streams made us fearful of advance and the guide then by throwing stones before made us conscious of the deep pool of water which terminated our way. Returning from this retired place the eye could scarcely be used, but where the ear was stunned by sounds, we lighted candles and then, stooping, creeping, stumbling, we proceeded through the hollows of the limestone into the bowels of the mountain. Stalactites covered our heads and embarrassed our feet but here and there, immense beds of sand offered steady footing and chambers formed by nature gave room for free motion. I crossed the river (Iringeth) with the guide to view some other parts of the cavern and proceeded a great way inwards. Here and there cavities ascended upwards many feet and let in daylight through chinks in the mountain and its sudden affusion every now and then over the objects below was very delightful in a ramble in what may be called darkness, for our candles were lost in the black space about us. After long admiration of the singular feats of nature in this place we left it and taking our course for the Inn, soon found ourselves before a table ornamented with excellent trout and eggs and ham."
Caves of South Wales, Stratford, T. , 1995
Proc.UBSS Vol.12, No.2, 1970 Standing, P.A. and Lloyd, O.C.
Descent 172, p.27, Chris Howes, The hidden resurgence [video]
The Last Adventure, pp.17-23, (1989), James S. Cobbett, Porth-Yr-Ogof - The Unreliable Memories of a Cave Diver
Descent 205, p.11, Martyn Farr, Porth's upper series
Brendan Marris Caves of South Wales
Cambrian Cave Registry entry 555
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