The tide rose and fell, not without having left its marks. One place in Istanbul to contemplate the vicissitudes of time is Hagia Sophia - Ayasofya in Turkish. Since it was first built in the mid sixth century, the building, repeatedly destroyed and rebuilt, has served, in order, as a Byzantine Christian Cathedral, or Roman Catholic Church, a Greek Orthodox Cathedral, an Ottoman Mosque and now a museum.

In 1453 Constantinople - which Istanbul has been called down the centuries, after Constantine the Great (272-337), another name being Byzantine - was conquered by the Ottoman Empire under Mehmed the Conqueror, who ordered the Christian church to be converted into a mosque. Mosaics depicting Jesus, his mother Mary, Christian saints and angels were either destroyed or plastered over. Islamic architectural features were added where the Christian ones used to be. Today a large part of those long-buried Christian wall paintings - the perfect embodiments of Byzantine art with their shimmering golden surfaces - has been brought to the daylight thanks to extensive restoration work.

Today these paintings and mosaics, partly erased, share the same vaulted ceiling with typical Islamic decorative patterns and calligraphy. The diffusion of light, sifted through the colored mosaic windows high above, has done less to illuminate the place than to enhance its holy ambience, making one more aware of the existence of an outside world, and an inner one.