Carreg Yr Ogof – Friday 19th October 2018

Huw Jones & Pete Jeffery
Words and photos – Huw

The original plan was for a trip into Craig A Ffynnon with Vernon but when Vernon had to drop out, I suggested a visit to the remote but interesting hill of Carreg Yr Ogof, on the Black Mountain. I’d wanted to explore the place for donkey’s years but had never quite got around to it. Pete runs the YHA at Llanddeusant, situated below the hill so this seemed like the perfect opportunity. The drive through the Beacons and around the Northern end of the Black Mountain is one of my favourites and I couldn’t help but stop to take the odd photo of the views up to the hills.

I arrived at the YHA at the appointed time to find no one around. Pete had had to sort a few unexpected things out and was currently at the tip! No problem as the weather was great and it’s a lovely place to just hang out. Pete turned up and quickly throwing his kit into a backpack we set off, in our wellies, on the hour’s walk up to Carreg Yr Ogof. There is plenty of height to gain in a relatively short distance but gallingly, the route actually starts off with a steep descent down a farm lane to the river! Starting up the other side, we climbed a bank to allow a herd of sheep to be driven passed, then soon turned off the lane to the farm and carried on upwards on a rough stoney track, that turned grassy before reaching the open hillside. The views are fantastic, with the Towi Valley spread out below us and the high peaks of the Black Mountain to the North, hiding the picturesque lake of Llyn y Fan Fach.

The gradient started to ease and Carreg Yr Ogof came into view, dotted with lots of old, small quarries. We carried on to the top on the hill (585m/1920ft) to get our bearings, where a large group of off road motorcyclists disturbed the peace somewhat. There are quite a few small caves spread around the hill, with lengths in the range of 20m-40m, plus a longer cave at 160m. We had planned to visit as many as possible but with the delayed start we decided to just check out the two best known caves of Ogof Carreg Yr Ogof and Ogof y Garimpeiros.

First we headed for Ogof Carreg Yr Ogof, the cave that the hill is named for. It’s all of 37m long but worth visiting. I’d loaded the co-ordinates into my GPS so we had no problem finding the entrance, where we got kitted up and headed in, Pete leading the way. The entrance chamber is rocky and bare. A short crawl then leads into the Main Chamber, where the floor is covered in many, many small stalagmites, a couple of inches to a couple of feet in height. They are unusual in that they are mostly white but each one has an orange top. The Main Chamber ends in a heavily calcited choke. A constricted route has been dug through on the right, leading to a very unexpected sight. Popping out of the choke, in front of you is a beautiful deep, green pool of water, looking not unlike a mini Dan yr Ogof Green Canal. There is plenty of pretty calcite on the walls and ceiling too. The passage carries on underwater but only for another 10m apparently.

Next, we made our way to Ogof Y Garimpeiros, the longest cave in the area at 160m. We’d noticed the location of the entrance as an interesting spot, on our way up to the top. The entrance is situated just above a sink and is covered with a green wheelie bin lid! Considering how loose the whole entrance area is, the shoring is pretty minimal, with just some thin metal bars and a few bits of rotten timber. Squeezing feet first through the entrance, it’s surprising how large the passage is so close to the surface. The extremely bouldery view before us set the scene for the whole cave. There is hardly an original, water-worn surface anywhere, with the walls and ceiling all angular facets, where the boulders have peeled off. Perhaps because it’s close below the surface, the walls and ceiling are almost completely covered in brown calcite. We joked that if it wasn’t for the calcite cementing everything together, the whole place would have fallen in!

Progress is made up and down boulder piles and includes a crawl through a choke half way along, before reaching the terminal choke. The stream is met at the base of the boulder piles and is a good size, considering it’s not far below the summit of the hill. The water has been traced to the Ffrwd Las resurgence on the Avon Twrch, right in the middle of the Black Mountain, a distance of 5.5km and 250m lower! That’s huge potential considering the equivalent figures for OFD are roughly 3.2km and 290m!

A really enjoyable day and somewhere I definitely want to return to, to check out the rest of the small caves. Best on a sunny day when it’s not too hot!