Barcelona is the capital and largest city of Catalonia, Spain. Some of Barcelona's most famous landmarks include the Sagrada Familia church designed by Antoni Gaudi, Montjuïc Mountain with attractions like the castle and cable cars, and La Pedrera apartment building also designed by Gaudi with wavelike balconies. The document provides pictures and information about additional popular places to visit in Barcelona like the beaches, parks, cathedral, and Camp Nou Stadium that is home to FC Barcelona.