The Collaborative International Dictionary of English v.0.48:

Sight-seer \Sight"-se`er\, n.
   One given to seeing sights or noted things, or eager for
   novelties or curiosities.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sightseer
    n 1: a tourist who is visiting sights of interest [syn:
         sightseer, excursionist, tripper, rubberneck]