What kind of cave st ructures hanging from the cavern roof?

Stalactites (calicte deposits) - their opposite numbers on the floor are stalagmites.

They can grow in three basic forms:

plain Stalactites - tapering, shaped like icicles,

Curtains (I believe aka 'Draperies' in USA), shaped a bit like curtains (!) and

Helictites - oddly-distorted things like bits of spaghetti, whose origins are still conjectural.

A cave roof can also exhibit particular erosion-forms such as box-work, a sort of tracery caused when the passage's formative stream filled it to the roof in its early development.