Tehuacan, Puebla is a small city very close to the state's capital. Despite it's small size (just 255,000 inhabitants) has a big history. There where found the oldest corn fossils in the world and there are a lot of archeological findings with more than 8,500 years.
The Valley Museum (or Museo del Valle in Spanish) belongs to Mexico's National Institute of Anthropology and History (INAH) and it's located in a part of the ex-convent "del Carmen". Upstairs is the Culture's House and Municipal's Library. It's windows show passages of prehispanic findings like pots, plates, necklaces and human remains.
From it's walls hangs maps and paintings that synthetize almost 10,000 years of history, and  you will find the relevance of "Coxcatlan Viejo", one of the empires that flourished around XV century in that part of Mexico.