Some of the earliest Umayyad "palaces" had almost no defensive purpose at all. They were built in the desert to be seen, not to survive a siege.

Durham Cathedral's ribbed vault, often called the first Gothic structure, went up 308 years after the same system was already standing in Cordoba.

No two Islamic buildings look alike. The Dome of the Rock, the Alhambra, and the Taj Mahal share almost nothing except one design instinct.