The interior of the cathedral consists of the central prayer area and several surrounding galleries, with the additions of side altars in the 16th century. The northern (facing towards the Palace of Facets) is the first gallery space, which is entered through the visitor entrance. This contains a famous Image of Edessa icon, attributed to the famous Russian icon painter, Simon Ushakov. The gallery is separated by a doorway from the main room, created in the 16th century by Italian architects using a striking azure blue color with gilt floral ornaments. The door wings are decorated with figures of ancient poets and philosophers (including Diogenes, Euripides, Plato and Homer).