Above the Celjska koča piste at the very peak of Tolsti vrh, about 2m from the registration box and hiking trail stamp, lies the entrance to the 10-metre deep chasm with a total tunnel length of 20m.
It was named after the peak. No karst formations are visible inside the chasm.
However, a draught can easily be felt, which indicates that the underground tunnels are somehow connected to the surface.
