The world's largest Gothic cathedral, built between 1402 and 1506 on the site of the great 12th-century Almohad mosque. The Giralda — the former minaret, now bell tower — rises 104m and you ascend by a series of ramps so gentle that the muezzin once rode a horse to the top. Inside: Columbus's tomb, Goya paintings, a 475kg silver monstrance, and the stunning Capilla Mayor altarpiece depicting 36 scenes from Christ's life.