the city & municipality of tenango del valle and its seat, tenango de arista, are located in the southern portion of the valley of toluca in mexico state, about 72 km southwest of mexico city and 25 km south of toluca. while the seat is officially named tenango de arista, it is more commonly referred to as tenango del valle, as this was the original name of the town. tenango del valle is best known as the site of the teotenango archeological site, which was a walled city inhabited from about 900 c.e. to 1550 c.e.