You are trapped inside a room with no way out except two doors, one leads to you greatest fear, one leads to your greatest treasure.
Also inside of the room are two twins, one of the twins always lies, the other always tells the truth. Both twins know which door is which.
If you can only ask one of the twins one question, not knowing which twin is which, what question should you ask in order to escape the room. You can only enter one door.