Deep in the Gürleyik hills 10km northwest of Safranbolu, the Bulak Mencilis Mağarası cave network has a 400m route open to the public; the actual caverns stretch for 6km. The deepest section of the route reveals a fine array of stalactites and stalagmites with inevitable anthropomorphic nicknames.
There are steps up to the cave and you should wear sturdy shoes as the metal walkway inside can be slippery and wet.
A taxi from Safranbolu costs ₺70 return including waiting time.