Built in 1765, the capital’s oldest surviving building has been a tavern, a brothel and a boardinghouse (sometimes all at once). Today it's a small museum offering a peek into Revolutionary War–era life. The evocative little garden in back is worth a mosey. The house was undergoing renovation at the time of research; it's due to reopen in late 2018, so check the website before visiting.
It was almost demolished in the 1950s, but a persistent (albeit false) rumor that Pierre L’Enfant used it as a workshop while designing DC saved it for posterity.