Tenochtitlan (Spanish: Tenochtitlan, Spanish pronunciation: ( mexiko tenottitlan) (listen) ), originally known as Mexico-Tenochtitlan (Classical Nahuatl: Mexihco-Tenochtitlan ( mei. ko te. not. ti. tan) ), was a large Mexica city-state on an island in Lake Texcoco in the Valley of Mexico. Founded on June 20, 1325, it was the capital of the expanding Aztec Empire in the 15th century until it was captured by the Spanish in 1521.

What was the name of the aztecs capital city? OK. Let's think. My stream of consciousness:
To answer this question, we should know that: Founded on June 20, 1325, it was the capital of the expanding Aztec Empire in the 15th century until it was captured by the Spanish in 1521. The answer is Tenochtitlan.