[Radek]

I think a more detailed explanation is needed because it it really is a common problem of all W&W players [img]graemlins/hehe.gif[/img]

The lever is a trigger that loads the dungeon. When you click it, the dungeon will be loaded and you will be placed into it. Look around immediately after being placed in the dungeon: You will see another lever, which will take you out of the dungeon. The mechanism is the same: click it, and the exterior will be loaded and you will be placed into it.
All dungeons in W&W are entered/leaved this way. Never expect that you will be able to enter some dungeon by clicking a door or something like that. Always search a lever. And every time you will need to leave the dungeon, search the lever (inside the dungeon) as well.