I went there and it was pretty cool !

Luckily an old man was selling mini-flash lights because it was dark in there.  A true experience.  Thx!

You must see Cheung Po Tsai Cave in Cheng Chau Island !

Its a real cool day trip, complete with nice ferry ride, intersting hiking, Cheung Po Tsai Cave is also a great thing to see.  After a nice day - You can have a wonderful meal from any of the many  restaurants in Cheng Chau's beach front area.  Yum !

the island has a very local feel and relaxed atmosphere. 

You should also check out the Bun Festival in May know as the Ching Chiu festival in Cantonese.