Fossil Fuels. However, producing solar, water and wind power plants and generators cost a lot of energy, generated by fossil fuels. The problem is that 'green' energy sources don't repay the amount of energy used to make them. Fossil fuels are bad guys, but don't think placing solar panels everywhere will stop the greenhouse effect. Not until their efficiency is high enough to produce more energy than is put into them.
Teotihuacan began as a religious center in the Mexican Highlands around the first century CE. It became the largest and most populated center in the pre-Columbian Americas. that is all I know about it
