This museum—located in the former monastery of Santa Cruz de Santiago Tlatelolco, behind the archeological site—opened its doors on December 15, 2011, after nine years of archeological and conservation work. The first floor displays murals and describes the excavation work, and the second shows a selection of archeological objects, including a particularly fine wooden vessel depicting Tlaloc, god of rain, one of the offerings placed there when the water cistern was sealed.

The importance of this water cistern (a constantly replenished store of drinking water) lies in the fact that its walls were covered in paintings that portray the daily life of the inhabitants of the lacustrine Valley of Mexico in the sixteenth century, following their subjugation by the Spanish conquistadors; some remnants of this artwork have been preserved. Dating back to 1536, this is the oldest mural in New Spain and was only discovered in 2002. Thanks to painstaking restoration work, around 50,000 fragments of painting have been assembled, covering an area of approximately 170 square feet, and record aspects of the life led by the indigenous peoples settled on the small islands of Tenochtitlan and Tlatelolco, as well as religious symbols from the early days of New Spain’s existence. The water deposit is believed to have been built immediately after the fall of the Mexica and was inaugurated at the same time as the Imperial College of Santa Cruz de Santiago Tlatelolco—the first institution providing higher education for indigenous students. The water flowed into this deposit before continuing its journey to Tecpan or the palace to provide a supply of drinking water and to irrigate the royal orchards.