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Ogof Ffynnon Ddu: Wales’ deepest cave

ANYONE looking for an adventure, providing you don’t suffer from claustrophobia, should know about Ogof Ffynnon Ddu.

Ogof Ffynnon Ddu 1, or OFD1 as it is more often abbreviated to, has one of the finest streamways of any cave in the country according to the experts, and is also Wales’ deepest cave.

The stream cuts through the jet-black limestone producing impressive cascades, deep pots and superbly scalloped walls. 

From the stream a route can be taken through to Cwm Dwr, OFD2 and the further reaches of the system, or you are able to climb up into the higher fossil passages to complete the Escape Route and one of the best round trips available.

In 1946 Peter Harvey and Ian Nixon dug an occasional flood rising above the main Ffynnon Ddu spring and discovered the main cave. This was quickly explored as far as Boulder Chamber. 

Boulder Chamber was passed in 1957 to reveal passages as far as Dip Sump. 

Dip Sump was passed in 1966 and then in 1967 a dry route through to Cwm Dwr was dug.

From the gated entrance a fixed ladder drops you down to the main passage, where to the right a descending passage takes you down to Gothic Sump. 

Ahead at the bottom of the ladder is the Cyril Powell Series, along sections of concrete footpaths in places, the remnants of an attempt to turn the cave into a showcave. 

On the left a shower inlet is passed at a junction, following this side passage leads over the top of Skeleton Chamber, where human remains were found by the original explorers. You can climb down into the chamber, but there is no way on.

The interior of Ogof Ffynnon Ddu

Passing over the top of Skeleton Chamber leads to Downey’s Cave. Back at the junction the main passage continues past The Font, a calcite pool formation and then proceeds to a junction with a fixed ladder up to the Toast Rack, a passage on the right here leads across Pluto’s Bath and down to the main streamway. 

Climbing the ladder takes you up to the Toast Rack, a series of fine gour pools, where a calcite flow can be climbed at the top to lead into Ogof Pant Canol. 

Following the main passage loops back towards the main streamway and a concrete balcony above the stream is followed to take you to an ascending passage with fine calcite floor. 

At the top of this passage is a junction, going up the calcite flow takes you to the Flood Escape Route, while following the bend the passage turns back on itself leading you down towards the streamway. 

A calcite flow on the left can be climbed to give access to Column Passage, with its fine calcite flows and large column. 

Continuing downwards to the sound of the streamway takes you to The Step, the general access point to the main streamway. Downstream will take you towards the sumps where the passage changes from a vadose canyon into low bedding passage before sumping. 

As you head downstream from The Step you pass a passage on the right that leads back to Pluto’s Bath, a traditional exit out of the cave to ensure people get a thorough soaking. 

Heading upstream form The Step takes you along some of the finest stream passage in the country, with passage over deep pots in the stream made safer with scaffold bars to walk across. 

Passages on the left lead into the Railton Wilde Series, a set of passages that head away from the streamway and then loop back. 

These passages are well worth the detour as they contain some fine formations and dried gour pools. Back in the main streamway you continue until a junction is met, ahead water issues from a sump, while taking the passage to the left leads to Boulder Chamber, Lowe’s Passage and the Waterfall Series.

Following the main passage leads past Lowe’s Passage on the right, with rope handline and then on a corner ahead on the right a climb up to the Waterfall Series. Continuing ahead leads to Boulder Chamber, where a large boulder choke is encountered. 

Once through the boulder choke a descending passage to the right leads down to Dip Sump, the way on is to the left to the connection with OFD 1 1/2. 

Back at the waterfall, a wet climb up or a traverse from further back up the passage leads into the start of the Waterfall Series. A choice of routes, the Wet Way and the Dry Way leads to a maze of interesting passages including a chimney up into Crystal Pool Chamber.

Back at Lowe’s Passage, a climb up assisted with the fixed rope starts the ascent into the upper series, but not before the passage drops to a crawl as you pop out at the bottom of a massive ramp of boulders. 

Height is gained quickly as you climb up the steep boulder slope until you approach the top of the passage. Here a climb up to a platform on the left leads to a series of bedding plane crawls and entry to Starlight Chamber. 

Back at the top of the passage the route continues ahead to lead you into Roundabout Chamber which boasts the Bees Knees calcite formations. A climb down through boulders leads some fine crystal walled passages before a bedding plane crawl – Roly Poly Passage is reached. 

Once through the bedding plane you enter the massive passages of the Rawl Series which ends in breakdown at Pi Chamber. From Pi Chamber a descent on the left leads to a discrete hole behind a rock that drops down a small and steeply descending polished passage to reach a traverse over a hole in the floor and the start of Bolt Traverse over the top of the main streamway. 

This 30m traverse assisted with the stainless steel cable takes you into a passage that leads to Rocky Holes Chamber, from here a passage to the left leads to a window over the main streamway – Airy Fairy traverse, but continuing to the right leads on to the Dug Out, a small squeeze into a large passage. 

The route is followed downhill over a calcite covered floor and a few static pools until you reach the end of the Escape Route as you regain the main passage in the entrance series.