Gökgöl Cave is Zonguldak's strongest single visitor sight. The cave runs deep into the limestone east of the city, with lit paths passing curtains of stalactites, stalagmites, travertine forms, and streams.
It is easy to visit by taxi or local transport from the centre, and it pairs well with the mining museum: one shows what people dug from the hills, the other shows what water carved there without help.