One of the most interesting empires of America. The Aztecs (at that time called the Mexicas) arrived in the valley where we today find Mexico City in the year 1253. As they didn't find any unocuppied land, they were forced to work as warrior slaves for the other tribes there. They proved to be very efficient at this task - once bringing 4,000 ears back from a battle as a present to their masters - just to prove that they'd won the battle. They managed to break free from their masters and take over another part of the valley and founded Tenochtitlan in 1325.

The first king was enthroned in 1375 - and from this date on, the warfare of the Aztecs escalated. In just a hundred years, the entire valley was under their control. In 1487 the great temple of Tenochtitlan was finished and about 20,000 people were sacrificed in three days to mark the occasion - all of them having their heart ripped out while still alive. (The rate of this is comparable to 6 millions in five years - anybody say WWII?- but was performed by only a handful of priests - estimations give a killing rate of one priest killing one man every 10 seconds.)

Just as quick as its rise was its downfall - in just one year, a very weak Spanish force lead by Cortes conquered Tenochtitlan that at the time had more than 200,000 inhabitants. The king at that time, Moctezuma II was sure that Cortes was the returning god, Quetzalcoatl. This made Moctezuma more or less surrender and also paralyzed him from doing anything about being captured and watching his people getting killed - which in the end his own people kill him.

With the destruction of the capital, the empire dissolved completely leaving almost no evidence of what was once the greatest city of the entire world - going to the main square of Mexico City gives you an idea though.