The Tehuacan-Cuicatlan valley is a basin of dry land in the mountains of southern Mexico, between the states of Puebla and Oaxaca, and it holds something unusual: the greatest density of columnar cacti in the world. Tall candelabra shapes, some of them ten metres high and centuries old, stand in forests across the hillsides, with agaves, yuccas and thorny shrubs around them, and in spring they flower white. UNESCO listed the valley in 2018 as a mixed site, for both its biodiversity and its human history, and it is also a biosphere reserve.
The history is remarkable. Caves in the valley, such as Coxcatlan, hold the oldest known remains of domesticated maize, small cobs dating back thousands of years, and the valley is regarded as one of the cradles of Mesoamerican agriculture. The inhabitants also developed an intricate system of canals and aqueducts to carry water across the dry land, and they harvested salt from springs at Zapotitlan Salinas, where the salt pans are still used. San Juan Raya, nearby, is a village on a hill with a sixteenth-century church and fossil beds with marine shells, evidence that this land was once under a shallow sea.
The ride here crosses dry, hot country. The federal highway between Tehuacan and Oaxaca is a good road, with curves through canyons and views of cacti in all directions, and the side roads to the villages are narrower, with potholes and occasional livestock. It is hot for most of the year, so ride in the morning, and carry water. Thunderstorms between June and September can bring flash floods in the dry riverbeds, so watch the sky. The desert light at dawn and dusk is warm and soft.
Teotitlan, the nearest sizeable town, has about seven and a half thousand people and some services, and Tehuacan, farther north, is bigger and has fuel in abundance. Fill up in one or the other, since the villages may not have stations. Try mole and tlayudas, the large crisp tortillas of Oaxaca, and drink plenty of water. The cactus forest is best seen in the early morning, before the heat builds.