Córdoba
Capital of the Medieval World
Córdoba was once the most advanced city on Earth. In the 10th century, when London and Paris were muddy villages, Córdoba boasted half a million inhabitants, street lighting, running water, 70 libraries, and a spirit of interfaith scholarship that preserved and advanced the knowledge of Greece, Rome, and Persia. The Mezquita—a mosque turned cathedral—remains one of humanity's greatest architectural achievements.