The main sight in town is this 10m-high pyramid perched atop a sheer cliff at the end of a very steep paved path that begins at the end of Avenida Tepozteco. Built in honor of Tepoztécatl, the Aztec god of harvest, fertility and pulque, the pyramid is more impressive for its location than actual size. At the top, depending on haze levels, the serenity and the panorama of the valley make the hike worthwhile.
Spotting the plentiful coati (raccoon-like animal) there is also a bonus.
Tepotzteco is actually some 400m above the town. Be warned that the path is tough, so head off early to beat the heat and wear decent shoes. The 2.5km walk is not recommended to anyone not physically fit. A store at the peak sells refreshments, but you should bring water with you anyway. Video-camera use is M$47. The hike itself is free, but to get close to the pyramid (and the view) you must pay the admission fee.