Cotahuasi Canyon, the deepest in the world at 3,354 meters, is more rugged than Colca. Since it was overlooked by the Spanish, there are few churches here. The Inca, however, built a highway along much of the canyon for transporting dried fish from Puerto Inca on the coast all the way to Cusco. Today, the ruins of these roads connect several villages that grow citrus fruits on thousand-year-old terraces.

The main town is Cotahuasi, which is a 12-hour bus ride from Arequipa at 2,680 meters. There are a few simple places to eat, sleep, and buy groceries here. The best is Alojamiento Chavez (Cabildo 125, tel. 054/21-0222), with a pleasant courtyard and friendly and knowledgeable owner.

The road continues up the canyon to the villages of Tomepampa, Lucha, and Alca. One good trek heads down the canyon from Cotahuasi along a path that crosses the river several times and leads, after a few hours, to the village of Sipia. Nearby is the thunderous 60-meter-high Cataratas de Sipia.

Trekkers can continue downstream to more isolated villages and ruins—and, with enough time, all the way to the Pacific, as the Inca did. Arequipa-based trekking agencies offer four-day treks to these areas. Arequipa-based Cusipata (Jerusalén 408A, tel. 054/20-3966, gvellutino [at] terra [dot] com [dot] pe) and Cusco-based rafting agencies lead eight-day Cotahuasi Canyon trips.

Buses for Cotahuasi leave in the evening from Arequipa’s bus terminal (12 hours) and arrive at dawn. Return buses to Arequipa leave Cotahuasi daily. If you can, travel this route during the day. The spectacular road passes over a 4,650-meter pass between Coropuna (6,425 meters) and Solimana (6,093 meters) before dropping into Cotahuasi.