Answer:
The Spanish built it as their capital of New Spain on the ruins on Tenochtitlán.
Step-by-step explanation:
Tenochtitlán had been the center of the Aztec people. The Spanish conquered the Aztecs and destroyed the city of Tenochtitlán. After destroying Tenochtitlán, the Spanish built Mexico City on its ruins. Mexico City became the capital of New Spain and was the political and cultural center of Mexico.