The Church of Hagia Sophia (Holy Wisdom) in Constantinople (now Istanbul) was one of the wonders of the late Classical world, built by the Emperor Justinian in the mid-6th century. It was the largest building in the world for almost 1,000 years, and its innovative use of domes and buttresses made the ceiling of the main dome seem to almost float in the air above the many windows that lit the building from every side. Not built by an architect, but by a geometer, it was the center church in Christendom for many, many years.
This icon is in a lunette over the southwest door of the church and it is a detail of the Virgin Enthroned with her Divine Son. It is worked in intricate mosaics, and in the full view shows the Emperor Constantine offering them the City of Constantinople and the Emperor Justinian offering them Hagia Sophia. Here we see the Virgin in a Classical style with a serene yet loving face looking at us, while she lightly holds the Lord of Glory. The Lord Jesus Christ sitting in her lap is the Lord of Life here and in the next world, and the Virgin was and still is His living throne.