Locally known as La Manquita ("the one-armed lady") because the south tower was never finished — funds raised for its completion were diverted in the 18th century to help the American colonies in their war of independence against Britain. Construction took 254 years (1528–1782), which is why the building is a layered jumble of Renaissance interior and Baroque facade.
Inside, look for the carved cedar choir stalls by Pedro de Mena and the small Gothic chapel that survives from the original mosque-cathedral. The roof is open to visitors via a separate ticket and gives a fine close-up view of the unfinished tower.