A vault can refer to: ^{britannica.com 3 1 2}

• A room, especially in a bank, with thick walls and a strong door, used to store money or valuable things in safe conditions.
• An arched structure, usually made of stones, concrete, or bricks, forming a ceiling or roof over a hall, room, sewer, or other wholly or partially enclosed construction.
• Figuratively, it can also refer to the sky, as in "the vault of heaven."