Temple of the Feathered Serpent, Teotihuacan

The third largest pyramid at Teotihuacan is the one with the best carving. Inside the walled Ciudadela, its stairway is lined with stone heads of the feathered serpent, still projecting from the facade nearly two thousand years after they were set there around 200 to 250 CE. Some 200 sacrificial burials were laid around it when it was dedicated, and in 2003 archaeologists found a sealed tunnel running beneath it, explored for years afterward.