The Romano-Byzantine basilica crowns Montmartre hill. Its construction began in 1875 and was completed in 1914. Admission is free, except for the crypt and dome (about € 5). For a fun ride, go to the Anvers metro station, walk to "Rue Tardieu" and take the "funiculaire" (a one-car train which brings you almost to the top of the hill).
Montmartre itself used to be a village outside Paris. The hill is famous for its architectural landmarks, its artistic life, and more recently, for the film, 'Amelie.' It is home to no fewer than 7 museums!