The Capitol Building complex comprises four areas, two of which can be directly accessed from the Capital Wasteland. The "Capitol Building" entrance from the west, in The Mall, exits into the Capitol Building west entrance area. The Seward Square entrance from the east is one of two doors into the Capitol Building west entrance.
Upon entering from the west, the other door into the Capitol Building east entrance is immediately ahead and to the right. The entrance to the third area, the Hall of Columns, is in almost exactly the same direction, east-southeast, but about six times further away, past the super mutant behemoth in the rotunda. At the end of the Hall of Columns are two stairwells; the door at the bottom of the second accesses the fourth area, the Conference Room.
A door in the northwest corner of Conference Room area leads back to a room one floor above the southeast corner of the west entrance area, but it is effectively a one-way passageway, as when the player goes through, the floor of the upstairs room caves in and crashes down to the room beneath. This also triggers a second battle between opposing forces in the rotunda (Talon Company and mutants, although these battles may differ by level).
Inside the Capital Rotunda, the Lone Wanderer will initiate a battle between the Talon Company and the super mutants. In the center of the rotunda is a super mutant behemoth. Several other mutants are also present, ranging from basic all the way to master. Two super mutant overlords are also present if the player has installed Broken Steel.
The entry-point to the Rotunda is on the west, just before the doorway is a passage north, that will lead to an average locked computer controlling the three Mark VIII defense turrets inside the Rotunda. It is set to not attack the Talon mercenaries, but the targeting data can be cleared. These rather hefty turrets will more or less clear the whole area of hostiles including the Behemoth without help from the player.
A Tales of a Junktown Jerky Vendor is on a desk in a row of four desks separated by screens; it is the one with the fallen filing cabinet. The row of desks is just north of the long hallway running east and west to either end of the area.
A pre-War book is located on the fallen cabinet next to the desk with the Tales of a Junktown Jerky Vendor on it.
Nuka-Cola Quantum found in a break room east of the desks with the pre-War book and the Tales of a Junktown Jerky Vendor.
D.C. Journal of Internal Medicine on the upper level. A Talon Company sniper is stationed on a bridge, and the book is on a railing facing south. If it is not there it was knocked down in the fire fight (this is common) just reload or look for it on the floor below.
When you fast travel from another location to the east entrance, an Enclavevertibird will pass and carpet bomb everything in front of you with mini nukes. This has also been observed occurring immediately upon exiting the Capitol Building using the east entrance. Be warned not to rely on them though, because they tend not to do a very thorough job.
Should you have the Broken Steel expansion pack, when you exit the Capitol Building, facing the Washington Monument and the trench networks, there will usually be a super mutant overlord patrolling the area, often on the steps to the left or right, (but sometimes to the right, just outside the door).
The Talon Company merc in the rotunda wielding the Fat-Man does not carry ammunition for it and fires it via script only once, at the supermutant behemoth. When approached, the merc will quickly and continuously switch back and forth between hostile and friendly, and can even be spoken to. He will never directly attack the player, even if fired upon. However, in the chaos of the skirmish with the supermutants, it is possible to be caught in the blast when the merc fires it. Should he perish, it is also possible for one of the other combatants to pick it up and not suffer any restrictions on its use against the player.
After installing Broken Steel the Enclave will establish a base to the left of the main entrance.
xbox360 The super mutant behemoth can sometimes spawn inside the small room with the turret control computer next to the rotunda. [verified]
ps3 Although it may well be intended by the developers to prevent players using the behemoth's size to their advantage, the super mutant behemoth cannot be damaged from outside the rotunda room. [verified]
ps3xbox360 The behemoth can sometimes spawn dead, with the Talon Company mercs shooting at its dead body. [verified]
ps3xbox360 The Deathclaw outside the Capitol Building inside the Deathclaw Cage can sometimes spawn outside the cage of which will have dead Enclave Soldiers around it. [verified]