Name of a HK movie?

I remember seeing a HK movie, perhaps produce in the late 80s-early/mid 90s. As i only watch a little part of it, i can only give a few hints. There is a man(in the present day hk) going down a pothole and pes through something(sorry, i don;t know how to describe it) and he is in forbidden city, (Qing dynasty era). He also leave forbidden city using the same way. May I know the name of that movie and who stars in it ? 10 Pts to the best answer,tks