Seward Square can be reached through the Metro, though it can also be reached through a sewer system from Pennsylvania Ave. It can be reached most easily through Anacostia Crossing station. It can also be accessed through The Capitol building from The Mall. A battle between Talon Company mercs and super mutants will be taking place on the Capitol building's steps, with exploding cars in the crossfire. To the east near the subway station (near Reilly's Rangers) is also the location of a scripted Enclave Vertibird drop-off with a sentry bot.
The Capitol building in the west, near the Seward Sq. Northwest map marker. This entrance to the capitol building is also the fastest way to reach the Presidential metro train to return to Adams Air Force Base, all you have to do is enter through the Seward Square Capitol Building entrance and go through the door to the right and the train is right there (Presidential metro and Adams Air Force Base only available with Broken Steel add-on, and the shortcut is only available after you've completed Who Dares Wins.).
A sky bridge east of the Capitol building (and accessible via the office building) houses a switch which will call in artillery to be fired across the square. This provides a way to take out some of the warring Talon Company mercenaries and super mutants. A sniper guards the switch.
If you have the Broken Steel add-on installed, a small sandbag fort with additional Talon Company mercs will appear in Seward Square Northwest, East side against a building, across the battlefield where super mutants and Talon Company fight it out outside the Capitol building back (East) entrance. A few loot items such as cherry bombs, 2 ammunition cases, 2 first aid boxes, suitcase etc., and a new holotape log titled "Talon Company merc log #1" on a shelf next to a first aid box. The log talks about Talon Company developments after the purifier was activated. There is also a chance that an Enclave vertibird will fly over the battlefield, dropping several Mini-Nukes and killing most of the mercs and mutants.
If you kill the mad preacher before he detonates the explosives, there are 5 mini nukes in the area below him. The first is directly under The Preacher's building on a pile of rubble. The second and third are under two barrels next to the slide. The fourth is in a shopping cart near the same slide. The fifth is on the merry-go-round. If Dogmeat is with you, having him ferret out the nukes will save you a great deal of search time. There are also 5 inactive frag mines that can be picked up without fear.
Several of the enemy encounters in Seward Square are set to spawn only when certain conditions are met. The conditions and enemies vary, but typically involve clearing the immediate area of enemies and re-traversing the square, and include super mutants and centaurs.
At 5th and Broadway is a Cinema that preserves a moment of the old world as the marquee hosts the movie titles One Wife Hold the Meatballs, Raz Baston and the Amazons of Xarn, I Married a Maoist and Hush Sweet Senator Hush.
The player can go out of the map by standing a barrel next to the chain-link fence and jumping on the barrel and then jumping over it.
Seward Square Park is a real-life location in the Washington, DC area. It is named after William Seward, Secretary of State under Abraham Lincoln and Andrew Johnson. The purchase of Alaska from Russia in 1867 was ill thought of during his lifetime, and known as "Seward's Folly" for this and his part in it.