Sainte - Chapelle where the Royals went to church. All made out of stained glass and built in the 13th century. It was one of the most impressive places I've ever been. The prison where many enemies of the royals were kept and later the prisoners of the revolution (which ironically were the royals, they were kept here before being beheaded). the oldest bridge crossing the Siene, built in the 1600's.