As they tour the Capitol building in Washington, some eagle-eyed visitors notice tiny, rounded doors at floor level — looking like fairy doors, or something Alice in Wonderland might have used after she shrunk herself. What are they? If you open one, you will see a small room with nothing but a faucet sticking out of the wall — useful for filling a bucket to clean the hallways. But why the need for such a tiny door? Why not use a regular broom closet?
The reason for the doors goes back to 1851, when a fire broke out in the Capitol building, in a room that housed the Library of Congress. A guard noticed the flames through a window, but there was no water source anywhere nearby, so he had to run downstairs to get some. By the time he got back, the library was in flames, a fire that would destroy more than 35,000 volumes, including almost two-thirds of the books that were acquired from Thomas Jefferson’s estate. Manuscripts, maps, artwork, all burned.
The government asked Captain Montgomery Meigs of the US Army Corp of Engineers to design a water system that would bring water into Washington and also supply it to the Capitol building to prevent future fires. He built an aqueduct system that brought fresh water in from the Potomac, and through pipes to faucets hidden behind those small rounded doors. The building now has modern plumbing and fire-suppression systems, but in a pinch they could always use the faucets that Montgomery Meigs installed behind those miniature doors (via Architect of the Capitol)