When you pay to go into the castle, ask for a torch (small fee) - or bring your own torch. Once you enter the castle, look for the tower in the bottom left corner - this is where you will find the entrance to the cave. Initially there are steps down but this then changes to a concrete slope and then you are onto wet, natural stone - slippery. The cave ends with what appears to be a blocked up well?
Drive through the village of Bethleham, up the hill, over the cattle grid and there is a parking place on the left. It is then an easy walk up the hillfort. Be careful though as the collapsed stone walls are very loose underfoot. The countryside here is beautiful. When I visited there wasn't a cloud in the sky and red kites were gliding silently overhead - bliss.
Visited 14.2.10. This site is difficult to find through a maze of unsignposted lanes. Eventually knew we were in the right place thanks to the lorry depot. Couldn't see an easy way past the depot and as it was a sunday there was no one about to ask. Just along the lane from the main depot / house there is what looks like a scrap yard. I parked here and looked for a way up the near vertical bank. In desperation i ended up climbing through the scrap metal, up through brambles to get to the top of the 'cliff'. Once on top of the bank the stone is easily seen, two fields away sticking up in a hedgerow. Mission accomplished! However, I would not advise anyone approaching the site the way I did as it is DANGEROUS. Please ask permission and find a safer route!!
At the entrance gate of Abermarlais Park there is an interesting stone, near which, according to a tradition related to me by Mrs. De Rutzen, the Welsh Princes held a council or* war. I was also informed by people in the neighbourhood that the spot was once haunted by the ghost of a lady in white.
*sic. From 'Folk-lore of west and mid-Wales' by J C Davies (1911).
This message board for Llangadog http://www.llangadog.com/messageboard1.html
has a photo of the stone and describes how it is also known as the 'Bosworth Stone', having been allegedly brought home from Bosworth Field by Sir Rhys Ap Thomas, as a souvenir of his side's victory (Abermarlais was one of his homes).
"Tomen y Rhos. A cairn located on a ridge (NE-SW), at a point where there is a slight levelling out of the ground.
The cairn is a turf-covered stony mound measuring 15m in diameter and 1m high. The cairn is ringed with rushes indicating the possibility of a ditch, tangible traces of which are visible on the W and S. The centre of the mound is marked by an excavation crater measuring 7m across and 1m deep.
According to local information (1967) two urns containing cremations were dug from this cairn in around 1825 (Arch. Camb. 5 (1854), 132-3.
(source Os495card; SN82NW3)
David Leighton, RCAHMW, November 1992
3. Remains of a round cairn situated within open moorland on the Mynydd Myddfai ridge. Circular on plan and measuring about 15.5m in diameter and now standing up to 1.2m in height. There is a large central crater, presumably the result of antiquarian investigation.
Source: Cadw scheduling description. 09/11/2004 FF"