The Archaeological Zone La Cruz is the clearest pre-Hispanic sight in San Juan del Río, set on a rise close to the modern city. The remains are modest compared with Mexico's headline ruins, but they give useful depth to a town better known for churches, wine, and colonial streets.
The site is worth adding if you are already spending time in San Juan rather than just passing through on the highway. Go for the city view and the chance to connect the area to a longer regional history.