Why do they call Mexico City the Mexico City?

This is by fat the most interesting and challenging question I have encountered, but let me make a long tail Short, when Cortes arrived to Mexico City, nobody had ever seen a City like this, let me try to tell you what they saw, a very big lake with different types of waters, and very different dephs, also towering volcanoes, and a beautifully city built on top of the lake, so sad but true he destroyed the city in order to finally conquer it, but the city became again the center of the kingdom, that is why they gave title of muy leal, y cristiana ciudad de mexico, la ciudad the city, was a way to distinguish her from the rest of the cities since she became the capital of capitals, from her, all the rest was conquered and made possible.