Tomb Raider (2013) - Tombs

Tombs are optional areas that Lara can complete to usually earn a lot of experience, Salvage and either a Treasure Map or modification to one of her weapons.

They are really only one room, where Lara needs to solve a puzzle that will grant her access to a chest with the above items. There are a total of 7 tombs hidden in the game, with one additional tomb added as DLC.