Tenochtitlan was the center of the Aztec government and religion. It was also a very big trading center. When the Spanish arrived in 1519, they guessed that 60,000 people came to the market in Tenochtitlan every day. People bought and sold many things there, including slaves (prisoners of war from states the Aztecs had taken over). The city had a huge pyramid called the Templo Mayor (Great Temple). The entire city was decorated with art, architecture, and stone sculptures.