Iron Key
From WikiRaider
The Iron Key is a key found in Tomb Raider II, in the level Venice.
The Iron Key is found in a small room, partially wet, opened by a switch in another area of Venice. The door closes behind Lara as she enters, and so she must climb upstairs with the key in order to escape, but there is a Brawler and a Doberman up there, guarding the exit switch.
This key unlocks a door in another part of Venice behind which is a switch that raises an Metal Gate, important in completing this level.