Hi, I had this issue too as all the cities look the same & the tooltips don't identify the city. However, if you actually click on the city tile (probably have to click twice: once will bring up the army, the second will cycle to the city on the tile) it will show you the name in the lower left info panel. Do that on all the cities until you find Constantinople (or Rome for the West). I then just made a note on the tile so it would stay labeled for me.