The town of Mexcaltitán was originally settled around 500 AD. It is laid out on an island in a circle, with all roads radiating from the central square. This is the same arrangement as Tenochtitlán (now Mexico City) where the Aztecs later moved. This layout is one of the reasons Mexcaltitán is thought to have possibly been the site of Aztlán.
This slide shows a depiction of Mexcaltitán we found in the Museo Aztlán in the center of the town.