Not marked on the 50,000 map, but is marked on the 25,000 as burial chamber, a good description of Tan y Muriau 700 meters north east possibly but not here, but, fallen broken stones probably won't fit on the map. The capstone is on the floor with about a sixth of it lying broken off to the side, any upright stones are also fallen, the whole thing is fallen.
Two rows of water filled drill holes cross the center of the capstone, I had thought they were for breaking up the stone but it might be that the locals used to put gunpowder in the holes during festivities, a kind of firework?
But even in it's destruction what's left is enough to see that this would have been an impressive burial chamber, on dimensions alone similar to Chun Quoit.
But yet again the siting of the stones is quite splendid, looking down across Porth Neigwl, aka Hell's mouth and on to Abersoch, and in the other direction, south west, up hill to Mynydd Graig with it's fort and hut circles.
Disappointing burial chamber unless you know what to expect, one for the completest.