[UPDATE BELOW] The outdoor labyrinth in the St. Thomas Parish (Episcopal) garden is barely visible from the street at 18th and Church NW, because it's elevated. (Thevideo below shows you how to find it.) It's a surprisingly peaceful place, given the vast amount of foot and car traffic passing by. The entrance is on 18th Street.
This is the only labyrinth in Washington, DC, that is open 24 hours a day, 7 days a week. Enjoy it while you can. The parish hopes to build a new sanctuary to replace the one that was destroyed by arson in 1970, an act of violence to which the congregation responded by building the peaceful garden that today houses the labyrinth and a fragment of the original sanctuary.