The vault is below and away from the nearest New York City Subway tunnels. The foundations of the Federal Reserve Building were constructed to withstand the weight of the gold vault and its contents, which would have exceeded the weight limits of almost any other foundation. Ninety-nine concrete piers, extending to the underlying bedrock, were poured to support the weight of the building. The vault walls consist of steel layers reinforced with concrete. The eastern wall of the vault is about thick while the other three walls are about thick. The only entrance is circular door inside a frame; when closed, the vault door forms a complete hermetic seal. The vault is additionally secured by listening devices, motion sensors, and cameras. , there had never been a successful break-in attempt, though a fictional robbery of the vault was depicted in the 1995 film "Die Hard with a Vengeance".