In this chapter, the term “Capitol Buildings” means the United States Capitol, the Senate and House Office Buildings and garages, the Capitol Power Plant, all buildings on the real property described under section 5102(c) (including the Administrative Building of the United States Botanic Garden) all buildings on the real property described under section 5102(d), all subways and enclosed passages connecting two or more of those structures, and the real property underlying and enclosed by any of those structures.1