Tehua­­can-Cuicat­lan Val­ley, part of the Mesoamer­i­can region, is the arid or semi-arid zone with the rich­est bio­di­ver­si­ty in all of North Amer­i­ca. Con­sist­ing of three com­po­nents, Zapoti­t­lan-Cuicat­lan, San Juan Raya and Purron, it is one of the main cen­tres of diver­si­fi­ca­tion for the cac­ti fam­i­ly, which is crit­i­cal­ly endan­gered world­wide. The val­ley har­bours the dens­est forests of colum­nar cac­ti in the world, shap­ing a unique land­scape that also includes agaves, yuc­cas and oaks. Archae­o­log­i­cal remains demon­strate tech­no­log­i­cal devel­op­ments and the ear­ly domes­ti­ca­tion of crops. The val­ley presents an excep­tion­al water man­age­ment sys­tem of canals, wells, aque­ducts and dams, the old­est in the con­ti­nent, which has allowed for the emer­gence of agri­cul­tur­al set­tle­ments.