Fitting a Circle on a Square
532-537 AD
532 532
29.00E41.00N
ARC

ISTANBUL, TURKEY
	One of the problems of building with domes is fitting them neatly on top of square buildings.
	The Romans mostly just didn't do it, though sometimes they used devices called "squinches," blocks that went across the upper corners of square buildings to make an octagonal surface on which the dome could lay. But squinches are ugly; they interrupt the smooth the rise of the walls to the top of the dome.
	Finally the Byzantines (or perhaps the Syrians) found the solution. It is called the "pendentive" and is based on the principle of the arch. Simply put, it smoothly bends and rounds the corners of a square building inward toward the top in order to form a round base for the dome.
	The best example of a pendentive dome is Hagia Sophia ("Holy Wisdom" in Greek) Church in Constantinople (now Istanbul, Turkey). The church was built in 532-537 AD by Emperor Justinian to replace a wooden roofed church that burned down in January 532 AD.
	Architects Isadorus, Miletus and Anthemius built a remarkable structure about as tall as the Arc de Triumph in France. Around the base of the huge dome are 40 windows that almost make it appear (from the inside) that the dome is floating on air. Around the main dome are several partial domes giving it support.
	When it was finished, Emperor Justinian supposedly claimed it was more beautiful than the temple built by Solomon in Israel. "Solomon," he said, "I have surpassed you."
	Hagia Sophia was made into a mosque in 1453 AD when the Muslim Turks conquered Constantinople. The minarets (towers) you see in the picture were added by the Turks.
