Far back in the story of human food, a cave in the Oaxaca valley holds some of the oldest evidence of the domestication of maize. In Guilá Naquitz, one of the caves of Yagul, excavations in the 1960s found small cobs of wild corn and squash seeds dated to around ten thousand years ago, showing how early hunter-gatherers began to cultivate plants. UNESCO inscribed the Prehistoric Caves of Yagul and Mitla in 2010 for that evidence.
The valley is also home to later civilisations. The Zapotecs ruled from Monte Albán for a thousand years, and Yagul was a fortified hilltop city, with a ball court, a labyrinthine palace of connecting rooms and a view over cactus-dotted plains. Mitla, nearby, was a religious centre, famous for its stone mosaics, geometric friezes made of thousands of cut stones fitted without mortar, which are unlike anything else in Mexico. The town is still a living Zapotec community.
The Tlacolula valley is a dry, open country of agave and organ pipe cactus, and mezcal is made here. Santiago Matatlán, a short distance away, calls itself the world capital of mezcal, and small distilleries offer tastings. Tlacolula's Sunday market, one of the oldest and biggest in the region, fills the town with food, livestock, textiles and crafts, so it is crowded but memorable. Hierve el Agua, a petrified waterfall of mineral deposits and natural pools, lies farther east.
The road from Oaxaca is Highway 190, a busy but good road, with trucks and buses and a lot of speed bumps in the villages. Sun and dust are strong in the dry season, from November to April, and the rains from June to September bring storms. Fuel is easy in Tlacolula, and you can eat tlayudas, big crisp tortillas with beans, cheese and meat, and drink hot chocolate with cinnamon. Take water and a hat when you climb to the caves.