The Collaborative International Dictionary of English v.0.48:

Capitol \Cap"i*tol\, [L. capitolium, fr. caput head: cf. F.
   capitole. See Chief.]
   [1913 Webster]
   1. The temple of Jupiter, at Rome, on the Mona Capitolinus,
      where the Senate met.
      [1913 Webster]

            Comes C[ae]sar to the Capitol to-morrow? --Shak.
      [1913 Webster]

   2. The edifice at Washington occupied by the Congress of the
      United States; also, the building in which the legislature
      of a State holds its sessions; a statehouse.
      [1913 Webster] Capitolian

WordNet (r) 3.0 (2006):

capitol
    n 1: a building occupied by a state legislature
    2: the government building in Washington where the United States
       Senate and the House of Representatives meet [syn: Capitol,
       Capitol Building]