In the middle of the chamber you will find a monolith with writings in Greek language. In order to read information carved in it, Lara must become better in that language. Look around the chamber. You will find three objects there that are called murals. You can use the instinct to highlight them. The instinct can be activated by pressing the right analog stick. Interactive objects will be highlighted with gold color.
Walk towards each of three murals found in the chamber (the fourth one can be found in the corridor leading to the next part of the level, but it can be used after you complete all actions in the chamber.
After interacting with three murals, Lara's skill in reading Greek will increase. Now you can walk towards the monolith and read it. Both in this chamber and later in the game reading the monolith will mark precise location of coin caches on the map. Open the menu and check the map, you will see a new marker next to the monolith. Walk to that location and press X, Lara will dig up some coins.
After digging the coins, go to the dead end of the corridor with fourth mural. Watch it, then walk towards the brick behind which you can see a faint light. Press the interaction button and Lara will use the axe to break the wall. Hit it three times and walk outside.