Barely a kilometre to the west of Acatepec lies the village of Tonantzintla (2200 m (7220 ft); population: 15,000; fiesta: August 15th, Día de la Asunción de la Virgen María). Whereas in the case of San Francisco de Acatepec it is the façade which is the masterpiece of the Poblano style, here in Santa María de Tonantzintla the same variant of
the Baroque finds supreme expression in the interior. In contrast the doubly-articulated façade of the church, kept predominantly red but with blue and white tile ornamentation as well as sculptures, is comparatively plain. The "extravagantly Baroque" interior of the church is quite unique, its breathtaking colouring and its mix of Indian and European elements being the work of anonymous local artists and craftsmen. Decoration embodying the mystic predilection for fruit, flowers and birds so characteristic of the pre-Columbian period, interwoven with Christian motifs, covers every available inch. Outstanding among the many features of interest are, in the choir, the orchestra of Indian musicians and stucco-work scenes with reliefs of Jesus, the Virgin Mary and St Christopher, and in the mid-section of the nave the picture of St Francis and sculptures of St James and St Anthony. High in the dome a bevy of cherubim appear to float earthwards from a flower in a sea of foliage. The pulpit arch exhibits some remarkable stucco-work - crowned devils spewing forth fruit, and ornamental atlantes.
Not far from the church stands a state-owned observatory (built in 1942) equipped with a Schmidt telescope. Inside are frescos by Miguel Prieto.