Over the last half-century Cinco de Mayo has morphed from a relatively quiet commemoration of the Mexican army’s victory over French troops in the Battle of Puebla on May 5, 1862, into a United States-centric celebration, usually centered around tacos and margaritas (and often mistaken for Mexican Independence Day, which is actually September 16). But this year Atlas Obscura is marking the occasion with a deep dive into Mexico’s culture from the amber mines of the southern state of Chiapas to the floating farms of Mexico City to the mysterious…