The medieval Romans looked back and believed Constantine had founded Constantinople with done divine aid:

The medieval Romans looked back and believed Constantine had founded Constantinople with done divine aid: 

“When Constantine the Great wanted to build the city and had to lay the foundation and to measure out the city, he went out own foot with his great men. And when he came to the Forum, the officials said to him: ‘End the walls here.’ But he said: ‘As long as the one who goes before me does not stop, I will not set the foundations.’ For he alone saw the angel. And when he had walked on foot with the whole senate as far the Exakianon, he saw there how the angel planted his sword, thus indicating that he would stop there. And therefore he set up the wall in that place.” 

Source - Accounts of Medieval Constantinople - The Patria. Translated by Albrecht Berger