It is impossible to know when we look back on the city now exactly where ideas first came from, that is, if ideas and practices came from Teotihuacan and then spread to other cities or came first from other cities and then spread to Teotihuacan afterwards. What we can know is that many of the features that existed in Teotihuacan were also present in other cities. Because Teotihuacan was the largest and most powerful city in the region for many, many years, it makes sense that many of the shared features in the different cities would have come from Teotihuacan as it traded with other towns or conquered them. Teotihuacan was also the most prestigious city in the region and so would have prompted other cities to copy it -- just like today when artists copy New York and Paris so that they can be seen as making the most modern art.

Among the things that Teotihuacan shared with other cities in the region was a grid system not terribly different from a modern American city, with streets crossing each other at right angles. Teotihuacan also had a water (or irrigation) system that was very common in cities in the region at that time. This water system channeled rainwater into storage areas so that water was available during dry seasons.

Teotihuacan was the home to a...

This is an especially important point because Teotihuacan was not a Mayan city. The fact that Mayans would copy the temple design of Teotihuacan for their own most sacred buildings proves how important the city was to the whole region. This is the same as today's Muslims using the design of Christian cathedrals when they build a mosque.
One way in which Teotihuacan was different than other cities in the region was that it was a multi-ethnic city. Researchers still do not know exactly what was the ethnicity of the people who built Teotihuacan, although they do know it was not Mayan or Aztec.

Teotihuacan rose to great power and stayed there for centuries because of its cultural accomplishments, its sophisticated system of labor, its wealth, its organization, and -- finally -- its religious dominance. Other cities in the region copied many things about Teotihuacan, and this admiration from other cities and peoples in the region was one of the essential reasons that Teotihuacan endured so dazzlingly and for so long.