The concept of nobility flourished in New Spain in a way not seen in other parts of the Americas. Spaniards encountered a society in which the concept of nobility mirrored that of their own. Spaniards respected the indigenous order of nobility and added to it. In the ensuing centuries, possession of a noble title in Mexico did not mean one exercised great political power, for one's power was limited even if the accumulation of wealth was not. The concept of nobility in Mexico was not political but rather a very conservative Spanish social one, based on proving the worthiness of the family. Most of these families proved their worth by making fortunes in New Spain outside of the city itself, then spending the revenues in the capital, building churches, supporting charities and building extravagant palatial homes. The craze to build the most opulent residence possible reached its height in the last half of the 18th century. Many of these palaces can still be seen today, leading to Mexico City's nickname of "The city of palaces" given by Alexander Von Humboldt.

What is a common nickname for Mexico City?