after you kill the queen, in the room with the chest, there is a lever to the right off the
chest which you need to flip...)

Serpent Temple?. After you kill Xydusa, you can open doors with lever on gong that is in Xydusa room, then go left to room with 2 chests and healing fountain. Above fountain is another lever to open way to maze

I know, it was supposed to be a reply, new on the board :=)