Pennsylvania Avenue/Seward Square Metro station (or, Penn. Ave/Seward Sq. Metro) is a fallen-in metro station. It can, however, be used by the player to quickly go between Pennsylvania Avenue and Seward Square.
Like just about any other metro station in Fallout 3, the outside of the metro is a few escalators going up/down to/from the doors to the metro. The outside of the metro is rather pristine compared to the inside.
The inside of the metro is significantly damaged, with the station platform buried under tons of rubble. To reach the other side, the player needs to navigate through the maintenance tunnels. Fro Seward Square, they come through an office at first, and then what seems to be an engineer's locker room, before entering the tunnels. Access to Penn Avenue is through the bathrooms, whose back wall collapsed. There are a few lockers spread throughout that hold some ammunition and supplies. The desks that you run into at first also contain some ammunition.
Penn. Ave/Seward Sq. Metro appears only in Fallout 3.