Other landmarks, many of which are listed on the National Register of Historic Places, include the International Temple, Embassy Gulf Service Station, Christian Heurich Mansion (also known as Brewmaster's Castle), Whittemore House (headquarters to the Woman's National Democratic Club), and the Phillips Collection, the country's first museum of modern art. The Richard H. Townsend House located on Massachusetts Avenue now houses the Cosmos Club. The Dumbarton Bridge, also known as the Buffalo Bridge, carries Q Street over Rock Creek Park and into Georgetown and was constructed in 1883. The Nuns of the Battlefield sculpture, which serves as a tribute to over 600 nuns who nursed soldiers of both armies during the Civil War was erected in 1924. The Mansion on O Street a luxury boutique hotel, private club, events venue and museum has been a fixture in Dupont Circle for over 30 years and includes over 100 rooms and 32 secret doors. The Brickskeller Inn & Bar has long been a popular bar in the neighborhood.