While the Hagia Sophia is probably not the oldest intact building in the world, it certainly comes close. Today, the (current) Hagia Sophia is 1478 years old, and has survived hundreds of earthquakes throughout history. Its age, size, magnificence, architecture and mystical atmosphere make it truly a unique place in the world. In this lecture we examine Hagia Sophia’s innovative domed construction, its myriad golden mosaics of Biblical and imperial scenes, and its lasting impact on later Byzantine and Muslim architecture.