This early Baroque gem, built in 1624, is one of the city's loveliest hôtels particuliers. Like much of the area, it fell into ruin until the 1950s, when it was rescued by the administration of French historic monuments (the Centre des Monuments Nationaux), which is based here. The recently renovated headquarters aren’t open to the public; however, you are welcome to enjoy the equally lovely garden. Stroll through it, past the Orangerie, to find a small passage into nearby Place des Vosges: Sully's best buddy, King Henri IV, would have lived there had he not been assassinated in 1610. An on-site bookstore (with a 17th-century ceiling of exposed wooden beams) sells specialized English-language guides to Paris.