Manhole cover...

Manhole cover - Wikipedia, the free encyclopedia:

"The first man-made object in space?
An urban legend claims that a manhole cover was accidentally launched from its shaft during an underground nuclear test in the 1950s, at great enough speed to leave the solar system. The story is based on a real incident in August 27, 1957 during the Operation Plumbbob nuclear tests, where a heavy steel plate cap was blasted off the test shaft at tremendous velocity, never to be seen again. It is not known if it actually left the atmosphere."