How to find it
From the junction of the D201 and the D590 near Aven Marzal, continue along the D201 towards Bidon. Not far afterwards the road bends to the left; just before the next bend (also to the left), the telegraph cables on the right of the road disappear into the woods. Park just opposite in the small space and enter the wood next to a telegraph pole just off the road, where a small path leads off. Very shortly afterwards a track leads to the left to quickly arrive at the limestone outcrop containing the entrances. (There's a more obvious track leading off from the road slightly further towards the Marzal junction; this is the wrong one!)
Description
One first comes across a hole about 2m round which looks to be a 40m pitch to the bottom of the cave. Further across the limestone outcrop, there is a drop providing a view onto an earthen slope below. Traversing around through the trees along the right-hand side of the hole gains a stance where one can climb down into a crack to arrive at the top of the earth and moss slope. Except in the driest of conditions---and even possibly then---a rope is advisable, as although the climb poses no serious difficulties, a slip would have serious consequences as the slope below plunges directly into the shaft beneath. From the bottom of the climb, traversing carefully around to the right leads to a ledge which can also be accessed (arguably more safely!) by a pitch of about 10m from a small window to the left up on the outcrop (2 slings, 2 krabs, 2 hangers and maillons: backup to thread well back and then small thread above window, followed by Y-hang from bolts). The ledge commands a fine view up to daylight (vaguely reminiscent of Aven des Neuf Gorges) and down to the bottom of the shaft; the first surface hole enters on the far side of the shaft as one looks across. From the top of the climb one has a fine view of the hole and any cavers ascending this pitch. From the ledge it looks about 30m to the bottom of the hole; the aforementioned 40m pitch joins the shaft on the opposite side from the ledge.
Apparently the pothole has no carbon dioxide problems.