HAGIA SOFIA elevates the power of faith in your empire. Every Cathedral you own reduces unhappiness by 6 citizens instead of 4 — and by 8 if Michelangelo's Chapel stands on the same continent.
For a thousand years, Hagia Sofia was the greatest church in Christendom. Its half-dome, its cascading light, its gold mosaics overwhelmed visitors into silence. Justinian called it the House of God. Its influence on mosque and cathedral alike is immeasurable.