Cordoba is known for this crowning Muslim landmark. The building is the size of three football fields. I am sorry for that description, but it does give size. It is a forest of marble pillars and red and white arches as impressive as any of the gothic churches of Europe. When Fernando III conquered Cordoba in 1236, he left the mosque intact. A 16th century archbishop constructed a cathedral inside. We are lucky this remains as it is truly magnificent.