The White House to Treasury Building tunnel is a 761-foot (232 m) subterranean structure in Washington, D.C. that connects a sub-basement of the East Wing of the White House to the areaway which surrounds the United States Treasury Building. It was originally constructed in 1941 to allow the evacuation of the president from the White House to underground vaults inside the Treasury in the event of an emergency.
https://en.wikipedia.org/wiki/White_House_to_Treasury_Building_tunnel