There are two contrasting man-made monuments to see here, a cairn and improbably sited hut circle, as well as Nature's own efforts in the form of some serious shakeholes.
The name is a bit obscure, as "Wydden" appears to have several different meanings. The most likely for a place-name element seems to be "tree", although generally it means that in the context of particular species, e.g. onn-wydden = ash tree; ffynidd-wydden = fir tree, whereas a non-species specific tree would usually be "coed".
However, a more interesting translation is "wood spirit", as in Bodelwydden ("Home of the Wood Spirit").
Hopefully someone who speaks Welsh can confirm or otherwise!
If it is "tree", the name would be something like "Small pit of the tree" (there's a non-"fach" version a little to the north, with a waterfall).
Pwll-yr-Wydden Fach cairn (SN82921508)
A cairn is located between two shakeholes.
It measures 10m in diameter and 0.5m high and is composed of loose small grade stones with some larger stones. The edge of the mound is grassed over. On the north-west lies a large slab and at the centre is a hollow 1.5m across and 0.3m deep.
Pwll-yr-Wydden Fach hut circle (SN82891510)
The hut circle is located at the bottom of a shake hole. Internally it measures 3.2m north to south by 2.8m and is bounded by a low stone wall of roughly coursed slabs and blocks. The wall measures 0.6m thick and survives to a height of 0.6m above the rubble strewn interior. On the west is a well marked entrance flanked on each side by boulders; they measure 1.1m and 1.3m long respectively and are separated by a distance of 0.45m.