as you go along you find more traces of passage on the walls and ground; the air seems to get more humid as you go along, and there's a slightly acrid odour tickling your nostrils. Luminscent moss grows in patches on the stone. The only sounds you hear for a while are your own and the faint dripping of moisture in the distance.
though eventually you pick up a faint scuffing sound ahead, like footsteps. *