The Dupont Circle Subway is the grand-daddy of D.C. Transit structures in terms of size and interesting features. It is located just below the very popular Dupont Circle and many feet above Metro's Dupont Circle Station. Until this station was built, all the transit companies operated streetcar lines throughout the city and suburbs. These streetcar tracks ran right down the middle of busy Washington streets. The Subway station was built in the 1940's to relieve traffic congestion in Dupont Circle that was caused, in part, by the streetcars' operation through the circle. Interestingly, the congestion caused by the streetcars was due to streetcar operations only on the west side of the circle, with tracks running in both directions, instead of operating in a circular, clockwise fashion like the rest of traffic.
The station was a mirror image of the traffic circle above: each train would complete a half-circle in a clockwise direction in the station before exiting. The platforms were also semicircular. This design ensured that passengers could emerge at the appropriate point in the Circle to catch a connecting bus without having to cross any streets. As there are four streets all intersecting at the Circle, there were seven or maybe eight stairwells into and out of the station. The streetcars traveled north-south along Connecticut Avenue and went underground at about O St., N.W. and reemerged at R St., N.W. After the station was closed, a vehicle tunnel was constructed using the remnants of the old station so that Connecticut Avenue now runs under the circle.
The station was closed with the demise of all the streetcars in the 1960's. In the 1990s, a brief attempt was made to turn the old station into a commercial operation, known as Dupont Down Under. The cheesy development quickly went bust, but not before renovating the entire west side of the subway station. In the process, the entrances on that side of the circle were pimped up from the original style.