San Dionisio

San Dionisio lies in the Tulancingo Valley, at 2,228 metres and about 3.5 kilometres southwest of Acatlán, the municipal seat. The ground is flat and its water belongs to the Metztitlán river sub-basin. It is a cool place: around 14 °C on average, frosty winters, and a 6.4 cm snowfall recorded in January 2008, the biggest since 1970.

In 2020 it had 1,240 residents in 307 homes (1,213 in 2010); nearly every house has electricity and piped water, and under 1% of the population identifies as Indigenous. The neighbouring seat, Acatlán, was one of the Tulancingo Valley towns that paid tribute to the Mexica, and in 1544 the Augustinians began its convent of San Miguel Arcángel. By the end of the sixteenth century the region had entered the age of haciendas, among them Mixquiapan, Totoapa, Tepenacasco and Cacaloapan; the locality of Mixquiapan is about 2.6 km northwest.

Low hills ring the village, such as Loma Larga (2,412 m), 2 km south, and Cerro Prieto (2,565 m), 3.6 km west, along with neighbouring communities like Loma Chica, Chauténco and Colonia Benito Juárez, all under 2.5 km. Every September the municipal seat holds the Expo Acatlán, selling dairy products and crafts, together with the feast of San Miguel Arcángel.