Vault 109 is an abandoned, closed-off vault. Not only is it surrounded with radiation, but it is filled with it too. Before it was in the state it is now, it had a comfortable relationship with Vault 84 with which they traded supplies. The cause of the radioactive leak is unknown. Vault 109 was a very high-class fancy vault, where most products inside are from Mary May, Ticknor and Fields and Fallon's. While it is a very high-end presentable vault, it does possess an armory containing a Fat Man and a set of T-60 power armor.