Located in the Plaza de la Reina, the Seu Catedral is probably most famous for its claim of owning the Holy Grail. Built in 1262, the Seu was raised on the site of a former mosque and displays a number of architectural styles, including Romanesque, baroque and gothic. The cathedral is open daily, though closed for siesta each day. Admission is free, but if you want to climb the gothic Miguelete tower or visit the Museo de la Catedral, you'll have to pay a small fee.