The Duma communicated with various parts of the city by messengers who rode in automobiles with guards of soldiers. These motors were driven at a terrific speed through the streets. One ran even more risk of being killed by them than by the bullets that were flying in all directions.
This page from the Hagia Sophia website is about the famous 15th century image of angel on the left side of the apse whose face was recently uncovered
Here's a page dedicated to this famous mosaic in the apse sem-dome of the great cathedral church of old Byzantium. It dates from the original redecoration of the church after iconoclasm ended.