Key of Poseidon
The Key of Poseidon is a key in the Tomb Raider Anniversary level Greece - St. Francis Folly. The key has a light-blue gem embedded.
To obtain the key, which is one of the four key opening the gate to the Coliseum, Lara has to overcome the obstacles in the Poseidon Room, in other words solve the Poseidon's Riddle. She has to first raise the water level by removing the small stone cube in front of the fish fountain one level up, to be able to pull the upper Underwater Lever, which will then open the floor grate holding a floating wooden platform. It gets stuck underneath a walkway. Lara then has to turn off the water completely by pushing the small stone cubes in front of both fish fountains, the one from before, and another one on a level below. Using her grapple Lara than has to pull the wooden platform to the opposite side, where, when the water level is raised again it can be used to reach a small alcove left of the chamber with the key. Via the protruding ledges Lara can climb into the chamber to claim the key.