^* The USNO was built on a low hill near the British embassy on Massachusetts Avenue, the site chosen to avoid light pollution from the then-small city to its south. Now it is surrounded by suburbs and a consequent vast amount of emitted light—and also as it happens by regiments of Secret Service guards, there to protect the onetime Superintendent’s Mansion, now the official residence (with a nuclear-hardened bunker beneath) of the American vice president.