Ogof Ffynnon Ddu

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Regions \ Wales \ Swansea Valley \ Ogof Ffynnon Ddu



Ogof Ffynnon Ddu translates from Welsh as "Cave of the Black Spring", after the name of its resurgence, Ffynnon Ddu. The name is often shortened to simply "OFD".

Cwmdwr means "Valley of the water" and this entrance gets its name from Cwmdwr quarry, in which it is located.


See descriptions of separate entrances.


Access to OFD I entrance differs from that to the rest of the cave in that a separate permit is required. A caver with an OFD II/ Cwm Dwr permit does not require to get this second permit. All Permits are administered by SWCC on behalf of the OFD Management Committee and the Countryside Council for Wales. Prior to January 2012, OFD I required cavers to be accompanied by a recognised OFD I leader.

Please note that in the interests of conservation, the use of carbide/acetylene lamps is not permitted in OFD. You must use electric lighting. Possibly the ultimate in conservation is the Virtual Caving Trip.

Detailed descriptions


Grid Reference: SN 848 153

Altitude: 220m

Ogof Ffynnon Ddu I entrance © Copyright Hywel Williams and licensed for reuse under a Creative Commons Licence. From Geograph

From the OFD I entrance, including all of OFD 1½ through to the base of Divers' pitch.

The entrance consists of a climb down on fixed ladders (2 sections, ~5m) which lands on the entrance gate. Going through the gate leads to another short fixed ladder (2.5m) which lands on the floor. Facing away from the ladder, the way onto the rest of the cave is straight ahead, right leads after 30m of passage to Gothic Sump.

Following the main passage the dimensions soon enlarge, passing the way to Skeleton Chamber on the right. After 5 minutes caving, Pluto's Bath and the Toast Rack are reached. The way on is to ascend the fixed ladder (2.5m) up the flowstone. Several corners later the route ends up 2m above the streamway on a concreted path complete with dubious fencing! Following this along, the stream is soon left and the passage starts to ascend. Approximately 20m after the stream is left there is a hole on the right at floor level, which can be followed to The Step via the Loopways.

Carrying on in the main passage, leads after another 20m or so to a sharp right turn. Left here leads to the Escape Route via The Dugout. Right leads down towards The Step. A small stream enters from the left, where it is possible to climb up towards Column Pool; the technique here is to lasoo the small stal with a rope! Carrying on past the climb leads to a short drop (2m) into an oxbow. Facing out from the climb, right is the other end of the Loopways, left leads after ~10m to The Step.

For safe condtions in the streamway, the water at The Step should be less than 15cm (6 inches deep). Downstream can be followed towards the other side of Pluto's Bath. Up stream leads over the two pots (with in-situ scaffolding bar bridges). Once over the pots there is a metal chain hanging from the left hand wall, this is an escape route and leads up towards the escape route via some in-situ steel traverse cables. Continuing in the streamway, pot 3 and 4 are passed. Eventually there is junction at stream level; on the left leads out of the streamway and towards Boulder Chamber. To the right the stream can only be followed a matter of metres until a sump is met.

Following the (normally) dry passage towards Boulder Chamber a rope is encountered hanging down from the right hand wall. This is Lowe's Chain and leads up into the Rawl series and the Escape Route. Continuing further in this passage a waterfall enters from the left (with the way into the Waterfall Series). Soon Boulder Chamber is entered.

Boulder Chamber is a mass of big boulders with the way on to the right, along a small crawl and then a squeeze down into a chamber containing a sump; Hush Sump. In wet weather this can overflow into Boulder Chamber and block the route. A climb back up leads to the other side of the choke.

Beyond the choke a slope leads down to Pot Sump and Dip Sump. The way on is to keep at the top of the slope and go straight on to enter The Connection. This passage is caver width and it is normally possible to walk upright.

One emerges from The Connection into a small chamber with a boulder slope ahead, turning right leads via some hands and knees crawling to a slight chamber where turning left leads fairly quickly into a chamber, normally with a small waterfall entering. The way on is to climb up the back right corner of the chamber into a passage. The climb is ~VD in climbing grades. It is also possible to climb a less exposed and easier climb 3m to the right of the climb in the corner into so small passage that leads via a slight squeeze to the top of the other climb.

From the top of this climb a passage is followed which leads to a step down with a large pot (~18m) on the right and the way on to the left. There then follows rifty passage where is is necessary to change level to go over/under jammed boulders. Here is Collapse chamber, which is probably still best treated with caution.

After Collapse Chamber a short crawl to the right leads to Letterbox Chamber. Here the way on is to climb up into the letterbox via the right hand side of the wall. There is a small bolt in place, although this is of almost no value since you can't grip it when you need it!

Through the letterbox turning left leads down in a rift, there are various small side passages which do not go very far, but the polish normally gives the correct route. The route is to follow the polished crawl downhill to a small chamber, then turn left back uphill in a gravel floored passage. This passage soon turns downhill again and the floor becomes limestone. Just before a T-junction is met an impossibly small looking passage enters under the left hand wall. Following this flat out squeeze the passage enlarges to just a squeeze for about 15m over a calcite floor with old gour pools in. If you fail to find this passage following the draught will lead to a window overlooking Divers' Pitch, with only a lone rawl bolt.

At the end of the low crawl described previously there is a thick rope belayed to a thread that leads, with the small stream down Divers' Pitch (~11m).

From the bottom of Divers' Pitch following the obvious way on leads to the Cwm Dwr area after ~100m of easy walking passage.

OFD II - Cwm Dwr

Cwmdwr entrance (the square gated hole, not the large opening above!) – Photo by Rhys Williams

Grid Reference: SN 857 156

Altitude: 350m

From the bottom of Divers' pitch, all of Cwm Dwr and to The Confluence. Awaiting description

OFD II - Top Entrance

Ogof Ffynnon Ddu II (Top Entrance) – Photo by Rhys Williams

Grid Reference: SN 863 158

Altitude: 425m

From The Confluence to beyond The Crevasse. Awaiting description


At the Crevasse, two bolts (with in-situ big maillons) enable a rope to be rigged for the ~5m climb onto the traverse. This traverse is over a ~25m pitch down to Pendulum Passage. Approximately 15m of traversing leads to the 10m pitch down. A 40m rope rigged from the top two bolts, across the traverse and belayed to the boulders at the head of the pitch just reaches the floor.

From the base of the pitch it is possible to carry on down (rope advised) into Pendulum Passage, but the way on to III is to follow the big passage from the base of the pitch. This leads up slope, passing over the brow. There is water falling from the left. The passage then leads back down to a squeeze between boulders into the passage continuation. Following for maybe 50m soon leads to a choice of routes: either traverse to stay at the level you are at or climb down then back up after 40m. Both ways involve exposed steps over holes.

Once over the holes the passage swings down and to the right, seemingly stopping. The way on is to climb up (or traverse in) to a passage about level with where the passage swings right. The climb is awkward (particularly on descent) and a rope is advised.

After the climb the passage continues ascending, passing a rope on the right. It then turns sharply right and a climb up leads to The Shambles. This big loose tower of rock is best climbed on the left when looking at it, descending on the other side about in the middle. There is plenty of loose rock and you'd be advised not to stand underneath the climb!

Turning left leads to an 2m climb up, the passage turns right, goes over some flowstone with water falling down the right hand wall and leads to the start of The Traverses. The first move onto the traverse is possibly the worst and involves teetering along a ledge on the left of the passage with a 20m+ drop to your right. After 5m it is possible to have feet to either side of the passage, the best route being obvious. After 50m of dead straight traverse an artificial floor is met, with traversing on the other side. Soon a rock pile is met, where the walls seem to spread out before the rock pile is met, the best way is to climb down or use the hidden hold on the left wall.

Beyond this rock pile is another 20m traverse, where the best way is climb down 2m before traversing outwards. At the end of this traverse the way on is to climb up the boulder slope and down he other side. Soon a boulder blockage is met, the way on is through the small hole on the left of the passage. Climbing/traversing down about 3m lands on a floor. Carrying on in the general direction that the traverses were leading in leads over a hole in the floor to a lower level and then up through a small boulder choke with a squeeze in it. This boulder choke goes up slightly, if you find yourself climbing down then you have gone the wrong way!

Popping out of the boulder choke, to the left is a short knotted rope that leads to the Paul Allen series, right leads down a boulder slope towards the streamway. A large hole down to the stream (20+m) is passed by a careful traverse to the left. Following the passage down further the next hole is passed by a scaffold bar bridge (Maypole Bridge). The high level passage continues, where a deep vadose trench to the stream is met turn left. 15 minutes after the scaffold bridge a chamber is met with water falling from the right hand wall. Following this water 5m down a solid rock slope leads to the streamway.

Downstream leads to the Niagra waterfall, upstream leads through fine streamway to Smith's Armoury. There are several places where the stream undoubtedly sumps in high water. Following up stream waist deep pools must be crossed, often with slippy sand banks around their sides. Blind white river trout can sometimes be seen. Often is is necessary to stoop in the stream due to boulders running in from the high level passages (which are difficult to find your way into). The stream is difficult to give a blow by blow account of, suffice to say the way is obvious and it is a very nice stream, different in character to the I and II streams.

About 30 minutes after entering the stream Smith's Armoury is reached where the stream issues from boulders. There is a rescue dump here which has a first aid kit as well as shelters/food for anyone unfortunate enough to be trapped by flooding.

Pwll Byfre, the main sink for Ogof Ffynnon Ddu at SN875166. This water is next seen at Smith's Armoury – Photo by Rhys Williams


The cave was first entered by Peter Harvey and Ian Nixon in 1946 following a dig at the site of an occasional flood resurgence. The streamway as far as Boulder Chamber was rapidly explored and later the high level passages were explored and surveyed. In 1957, Boulder chamber was passed and Dip Sump revealed. It was not until 1966 that Dip Sump was finally passed by divers and the vast extensions of Ogof Ffynnon Ddu II explored. In 1967 a dry route out of the extensions through to Cwmdwr Quarry Cave was found. Some months later, the top entrance was dug open at a site identified inside the cave as being close to the surface - no evidence of it existed above ground. The route to Ogof Ffynnon Ddu III and the current limit of exploration at Smith's Armoury was reached soon afterwards.


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