Reserva de la Biosfera Tehuacán-Cuicatlán

Reserva de la Biosfera Tehuacán-Cuicatlán, a UNESCO site, protects the world's most diverse columnar cacti—81 species, including the 15-meter cardon—in a transitional desert ecosystem. It also safeguards the earliest evidence of maize, squash, and chile domestication, a history 30% older than that at #7 Sumidero Canyon. The reserve's plant density, with 3,000 species per 500 square kilometers, is higher than the typical Mexican desert reserve. This site is a living archive of arid land evolution.