The second and third floors are the only accessible floors. The second floor can be reached from the ground by ascending metal wreckage. The building is connected to a small section of the city sewers nearby, which leads to the third floor of the building. The majority of the inner walls are destroyed.
Part 2 of the Nostalgia challenge can be accessed on the second floor on the "Office of the Treasurer" terminal. Unusually, this may not add a note to the PipBoy, although reading the terminal still counts toward the achievement. The terminal shows messages regarding the treatment of anti-nuclear-weapon protesters, one of whom may be Sunflower Summers.
There may or may not be two deathclaws outside this building. Their appearance depends on whether or not the marked men in the building just northwest upon entering the area after detonating the warhead are killed.