The Collaborative International Dictionary of English v.0.48:

Arcadia \Ar*ca"di*a\, n. [L. Arcadia, Gr. ?.]
   1. A mountainous and picturesque district of Greece, in the
      heart of the Peloponnesus, whose people were distinguished
      for contentment and rural happiness.
      [1913 Webster]

   2. Fig.: Any region or scene of simple pleasure and
      untroubled quiet.
      [1913 Webster]

            Where the cow is, there is Arcadia.   --J.
                                                  Burroughs.
      [1913 Webster] Arcadian

WordNet (r) 3.0 (2006):

Arcadia
    n 1: a department of Greece in the central Peloponnese