|The following is based on Fallout: Brotherhood of Steel and has not been confirmed by canon sources.|
The Garden is a leisure facility in the Secret Vault, Vault-Tec's private Vault where its members intended to survive the apocalypse and later enter the world having useful technology. The Garden includes a large beautiful park with trees and grass.
Some time after the war, the Secret Vault was torn apart by a local civil war between Vault-Tec scientists and Blake, the chief security officer, who believed the researches with FEV and radiation, conducted on living subjects, including humans, are "evil". Their battles led to a major explosion that devastated a large portion of the Vault and enabled some species of radroaches and Deathclaws, native to the Vault, escape into the wasteland, at the same time allowing radscorpions and rats invade the Vault.
Many people, including security officer Patty and chief scientist Dubois hide in the Garden, looking for a way to survive. It became the only safe haven the inhabitants of the Vault now have. When the Initiate was wounded by Attis, lost his hand and was left to die in the ruins section, Mary, a young girl who was searching for her mother's lost ring, found him. She helped him to access the Garden, where the scientists used prototype regeneration technology to literally grow him a new arm.
The place was inhabited by many people, including scientists. The residents were Mary, Patty, Dubois, and a scientist named Ching Tsun. They used regeneration technology, the CALIX computer main terminal, weapons manufacturing and some brahmin captured from the wastes to ensure their safety.
When the Dubois gone missing in the ruins, Patty become a new leader of the survivors. She decided that the time to leave the doomed Vault has come, and asked the Initiate to help them shut down the auxiliary vent, so they could escape through it. He helped them, but when the people started to leave, Super Mutants attacked.
With the help of Initiate and Ching Tsun, who stayed to fight the attackers, the people of the Vault succeeded in escaping their home to a new life in the wasteland. Only Patty is later revealed to remain in the Vault, in order to insure its researches will be destroyed and won't plague the world above.
The Garden is call "Snoresville" by Mary, due to the monotonous routine.
The Secret Vault's Garden appears only in Fallout: Brotherhood of Steel.