The Great Pyramid of Cholula is the city's essential sight: a huge pre-Hispanic ceremonial platform now mostly buried under earth, grass, and colonial history. From outside, it looks like a hill with a church on top; inside and around it, tunnels and excavated sections reveal the scale of the structure.
The archaeological zone is best visited slowly. Walk the base, look into the exposed masonry, visit the museum, then climb to the church for the view over Cholula and, on clear days, Popocatépetl.