Coahuila is a big northern desert state with two surprises in it.
The first is Cuatro Ciénegas: a basin of spring-fed pools in the middle of the Chihuahuan desert containing stromatolites — living mats of cyanobacteria of the kind that oxygenated the atmosphere three billion years ago — and dozens of species found nowhere else. NASA has studied it as an analogue for early Earth and for Mars. The water is being drawn down for alfalfa, and some pools have already gone.
The second is wine. The Parras valley has been making it since 1597, which makes Casa Madero the oldest winery in the Americas, older than any in California or Chile.
Saltillo is the capital, known for its sarapes and for a cathedral with one of the finest churrigueresque façades in the north. Torreón anchors the Laguna conurbation. Piedras Negras faces Eagle Pass on the Rio Grande and claims, with some evidence, to have invented the nacho in 1940.
General Cepeda has dinosaur fossil beds and rock art nearby.
