In 1864, archaeologists excavating beneath Mexico City discovered a vast underground network of tunnels and chambers, believed to be an emergency refuge built by the Aztecs before the Spanish conquest. The city, named Teotlacapan, featured intricate carvings, ventilation shafts, and traces of freshwater sources. Some scholars speculated it was a last stronghold against invaders. However, as Mexico City expanded, the tunnels were sealed and lost. Modern historians, aided by digital archives and Wikipedia page creation service experts, have worked to document its existence, though no recent excavations have been permitted. The mystery of Teotlacapan endures.