This is one of the most important archaeological find pertaining to the pre-columbian era. It is the ruins of a city which was at its apex during 1st millennium CE. It is said that, it may have at that time inhabited more than 100,000 inhabitants making it one of the largest human dwellings anywhere in the world. Its huge residential area for some reason is called the 'avenue of the dead'. It also has some huge and breathtaking pyramids dedicated to Sun and Moon. There are many small talud-tablero platforms along the avenue of the dead which were believed to be tombs by Aztecs. Many murals showing images of gods and of daily life have been excavated from the site.