This page of the Biomutant guide you describes the side quest Old World Vaults. Here we have described all the treasure vaults you must explore to complete the quest and earn rewards.
Starting the quest
How to start: Reach one of the vaults.
Reward: Equipment acquired during vault exploration.
To start the quest you must reach one of the vaults available in the game world. A key is required to open the vault.
Location: North of Bricktown.
How to get the key: Defeat Bling Sizzlefluff.
The entrance to the vault is in a buried tunnel. You must first go through a metal door, which should be no problem to open. Then just find the door and use the key to open it. This way you get into a vault full of raw materials and upgrades.