[55] Meanwhile, in the southwest of Europe, the world of Islam was shining a highly cultured and influential light into medieval Europe. In the year 711, North African Muslims crossed the Strait of Gibraltar, conquering and converting. For the next seven centuries, much of Spain was ruled by these Moors.

[56, Moorish rule, 711–1492] Córdoba was the leading city of Muslim Spain. Arguably Europe's cultural capital in the 9th century, it had perhaps ten times the population of Paris.

[57, Mezquita (mosque), late 8th–10th century, Córdoba] Its massive former mosque dominates the tangled medieval city that surrounds it. Grand gates lead to the courtyard. Inside is a forest of delicate columns and horseshoe arches built ten centuries ago. The columns and arches seem to recede to infinity, as if reflecting the immensity and complexity of God's creation. Under their rule, this distinctive style of the Moors spread throughout southwestern Europe, or the Iberian Peninsula.

[58, Alhambra, 14th century, Granada, Spain] Granada's Alhambra, the last and greatest Moorish palace, shows off the splendor of that Muslim civilization. The math necessary to construct this palace dazzled Europeans of the age.

[59] The décor was exquisite, artfully combining both engineering and aesthetics…water and stone. In the throne room, the sultan would sit regally, under an awe-inspiring wooden ceiling. With 8,000 pieces inlaid like a giant jigsaw puzzle, it symbolizes the complexity of Allah's infinite universe.

[60] Arabic calligraphy, mostly poems and verses of praise from the Quran, is everywhere. Muslims avoid making images of living creatures in holy spaces — believing that's God's work. But decorating with religious script is fine. One phrase: "only God is victorious," is repeated thousands of times — as if a sacred visual chant — throughout the Alhambra.

[61] By the way, while churches portray people like this…in mosques, rather than images of saints and prophets, you'll see geometrical designs and calligraphy. This explains why, historically, the Muslim world excelled at non-figurative art, while artists from Christian Europe focused on painting and sculpting the human form. Artful Arabic calligraphy generally shows excerpts from the Quran and quotes from Mohammed. As a church would show portrayals of Jesus and God front and center, in a mosque, elaborate medallions of script high above the prayer niche read "Mohammed" and "Allah."

[62] Christian forces slowly pushed the Moors back into Africa and re-conquered Spain. With their "Reconquista," Córdoba's Mosque became a Christian church, with a huge chapel planted in its center. Sevilla's Alcazar palace soon housed Spanish kings. But, even after the Reconquest, as Moorish artisans worked for Christian rulers, that Muslim legacy lived on in Spain.