Packed with stunning buildings, the entire historic center of Córdoba has been included on the list of UNESCO World Heritage Sites. At its peak, Córdoba was home to Christian, Jewish and Muslim communities—a multicultural city long before that concept was commonplace. A former mosque, the Mezquita is now a breathtaking cathedral with a forest of columns topped by red and white horseshoe arches. The alleys of the Jewish Quarter are as walkable as they were centuries ago, and a stroll across the Roman Bridge spanning the Guadalquivir River provides beautiful city views. The gardens in the medieval Alcázar castle make for a fine respite from sightseeing.