Two Rooms, Some Treasure, And A Monster
Riddle: There are two rooms in front of you. On the door to each room, there is a sign; only one of the signs tells the truth. The sign on the door to the first room says, "There is treasure here. A monster lurks in the other room,". And the sign on the door to the second room says, "The treasure and the monster are in different rooms,". Where is the treasure?
Answer: The treasure is in the second room. If the first sign is true, then the second sign is true, too. This contradicts the terms of the game. Therefore, the first sign is false, and the second sign is truthful.
Source: https://www.riddles.com/index.php/11435
