Dan-yr-Ogof, DYO, Under the Cave, Dan yr Ogof Resurgence, Darren-yr-Ogof, Cliff of the Cave, Tarren yr Ogof, Llan-yr-ogof, Cave church, Dan-yr-rogof, Llenvah Spring
NGR: SN 83820 16000 225 m.asl
Powys
, Northern Outcrop - West (Black Mountain)
map using leaflet map:
Rising
Cave
Access
The first part of the cave is a show cave and can easily be reach from the Sennybridge-Swansea road. The cave is owned by the Dan-yr-Ogof Cave Co. Ltd and the cave is managed for access by cavers by the Dan-yr-Ogof Cave Advisory Committee. Only parties accompanied by a Warden (Leader) appointed by DYOCAC may go beyond the show cave.
See caving.wales for current Access arrangements
Description
First recorded exploration by the Morgan brothers in 1912,
The river cave can be followed for 120 metres to a sump. The show cave is 520 metres long and leads to a series of four lakes beyond which is a complex series of passages and chambers ending in a long crawl. In 1966 a major extension to the cave was discovered some one mile in length. Two further extensions were subsequently discovered giving the cave a length of over 9 miles. The old cave and first part of the new extensions run in a SW direction, the known passages then running north.
History
Marked on Kitchin's 'accurate map of Brecknockshire' (~1770) as Llenvah Spring; Dan-yr-rogof on Greenwood's map(1828). First recorded exploration by the Morgan Brothers, 1912. Extended by The Dragon Group in 1939, SWCC, CDG 1964,...
Hydrology
35oz. fluorescein appeared in 50 hrs from Sinc y Giedd (Harvey, 1948). In very wet conditions, fluorescein from Waen Fignen Felin to DYO in 8 hrs (Hunt, 1963). Spore tests from Twyn Tal-Ddraenen, Carreg Lem, and Lost Valley Sink. Peaty brown water is noted in flood, milky in drought (perhaps due to collapse of sand banks), and sometimes red (perhaps from draining of iron-rich pools).
35oz. fluorescein appeared in 50 hrs from Sinc y Giedd (Harvey, 1948). In very wet conditions, fluorescein from Waen Fignen Felin to DYO in 8 hrs (Hunt, 1963). Spore tests from Twyn Tal-Ddraenen, Carreg Lem, and Lost Valley Sink. Peaty brown water is noted in flood, milky in drought (perhaps due to collapse of sand banks), and sometimes red (perhaps from draining of iron-rich pools).
The Rising
Washing Machine
Great North Road
Mazeways
Survey
Old cave. G.Platten. 1938. Plan only. Private
Old cave, J.H.Davies. C.R.G. grade 4. 1952 Plan only. Private
Old cave based on various surveys with new additions, A.Coase C.R.G. Grade 4, Plan only. Limited publication
Provisional survey of 1966 series. D.Thomas C.R.G. Grade 1 and Plan only. Published privately
Show cave survey. N.S. Christopher 1967. C.R.G. Grade 6c Plan and section. unpublished
Wessex CC Jnl 109, 1967, p.141
Composite survey of all known cave. Plan only based on above surveys, A.Coase and D.Judson. Published. SWCC
Jones, Theophilus, A History of the County of Brecknock, v2, p.658 (1809) "On the north of the Tawe a little below the fall of the Tawyne is a rock called Daren yr ogof, or the rock of the cave, from this springs up at once a sufficient quantity of water for turning a grist mill at all seasons of the year; this brook, or rather river, called Llynfell, from Llyn a liquid and ell a common termination: after crossing the turnpike road from Brecon or Trecastle to Swansea: soon falls into the Tawe, the inhabitants observe that in a rainy day this river does not perceptibly increase, but that on the following day it becomes muddy, and the quantity of water is considerably greater; there is nothing singular in this, the rain falling on the mountain above has not only a very considerable depth but many varieties of soil to penetrate before it reaches the hollow of this cavern, and consequently a long portion of time is required before the additional water can swell the common current..."
Cambrian Travellers Guide, Nicholson, G., 3ed,p.459 1813;1840, "On the N. of the Tawe a little below the fall of the Tawney is Daren-yr-ogof, "the Rock of the Cave;" from this issues a very strong stream, but not equal in quantity to the spring at Ogmore, in Glamorganshire "
A General View of the Agriculture & Domestic Economy of S.Wales (London, 1814), Davies, W., v1.p.110 "the peaty colour of the water at this time proved that it had connection with the turbary hollows...to the west"
The Geology of the South Wales Coalfield, Part V, A.Strahan, T.C. Cantrill, 1904, p.20, 'The Llynfell issues from a cave at Dan yr Ogof...but few dry caves have been discovered'
Handbook fo Cardiff an District prepared for the use of the British Association, Ivor James, 1904. 'a cavern, one of three...until recently...beautiful spectacle of stalactite encrustation...From the central of these caves, the River Tawe emerges'
British Caver, 2, 1937, p.12, 42
Yorkshire Ramblers' Club Journal, Volume 7 Number 23, pp.52-61, Dan-Yr-Ogof and the Welsh Caves and pp.79-88, Cave Exploration
British Caver, 3, 1939, p.97
British Caver, 4, 1939, p.70
Dan-Yr-Ogof Caves, Swansea Valley, Official Guide, pp.29, Llew.E.Morgan, 1939, includes the definitive account of 1912 explorations by the three landowners and their gamekeeper, with photos
British Caver, 5, 1940, p.21
British Caver, 6, 1941, p.50
British Caver, 6, 1941, p.57
British Caver, 11, 1943, p.57
CRG nl 15, (1948), P.I.W.Harvey, Notes on water tracings carried out from Pwll Byfre and Sink-y-Giedd
SWCC, 1949
SWCC Newsletter, Jun 1950, different colours of water noted - red, brown, milky...
records
