Tenochtitlan is located in what is now the Federal District in Mexico, and was built on an island in Lake Texcoco. The capital of Mexico is built on top of the ruins of Tenochtitlan, but many ancient structures from the original city still exist. The city of Tenochtitlan was founded in 1325, and according to Aztec legend, this region was chosen on the basis of an ancient prophecy which stated that the Aztec capital would be built where the people saw an eagle eating a snake, while sitting on a cactus. At its height, the city of Tenochtitlan was home to almost 250,000 people, and covered around thirteen square kilometers. The city was divided into four zones, each with twenty districts, with public buildings such as temples and schools located in the center of the city. The palace of Montezuma, the fifth emperor of the Aztec Empire, was also located in the central area of Tenochtitlan, and contained zoos, botanical gardens, and aquariums of both salt and fresh water.