In 2013, the basement bar of the emblematic Hotel Posada de la Misión was remodeled so the floor could be lowered a few centimeters. During the course of the otherwise routine work, a deep hole in the ground opened, revealing a long-forgotten mine.

Mining engineers were called to explore the site, and they concluded the mine had likely been worked in relatively recent history, perhaps during the years when Mexico was the Viceroyalty of New Spain. It wasn't until the Instituto Nacional de Antropología e Historia (National Institute of Anthropology and History) became involved that it was discovered the mine was pre-Hispanic. It's likely the indigenous Chontal people hid it to prevent the Spanish from plundering its riches.

Today, anyone can visit the mine via a guided tour. The tour begins in the room where the hotel bar once was. The guides are able to point out the veins of silver and gold that still streak the underground space. Many of the tunnels haven't yet been explored, but those that have been fitted for touristic purposes are so spacious, visitors can even rappel down some of them.

The final part of the tour leads to the new hotel bar, which is located in front of the pool. There, you can see a mural of Emperor Cuauhtémoc that Juan O'Gorman, (the same man who created the murals at the Central Library of the National Autonomous University of Mexico), made for the hotel.