The city where the Caliph built Europe's greatest library — a mosque the size of a city block that was turned into a cathedral but never lost its forest of 856 red-and-white striped arches
Córdoba is a city of 325,000 on the Guadalquivir River in Andalusia. Under the Umayyad Caliphate of Córdoba (929–1031 CE) it was the largest city in Europe — population estimates reach 500,000 — home to 3,000 mosques, 300 public baths, and Europe's first library with 400,000 manuscripts. The Mezquita-Catedral (UNESCO World Heritage), begun in 784 CE, is one of the world's most remarkable buildings: 856 columns of marble, onyx, and granite supporting red-and-white striped double arches, with a 16th-century Gothic cathedral inserted inside by Emperor Carlos V.
Córdoba was the capital of Roman Hispania Ulterior Baetica — Julius Caesar was governor here in 61 BCE, and the Stoic philosopher Seneca the Younger was born here around 4 BCE. Under Abd al-Rahman III, who declared himself Caliph in 929, Córdoba became the cultural capital of the western world; the philosopher Averroes (Ibn Rushd) and the physician-philosopher Maimonides were both born here. In 1236 King Ferdinand III of Castile reconquered the city, and the Mezquita was immediately consecrated as a cathedral — a layering of religions unique in the world.