The Amphitheatre is a huge natural bowl cut into the red rock of the Quebrada de las Conchas, a half-circle of towering sandstone with the acoustics of a concert hall. The walls are about thirty metres high, and the narrow opening lets the sound bounce around in a way that makes a single voice carry. Local musicians often play here, with charango and guitar, and a few sing for tips. It is an extraordinary experience to hear a folk song echoing around the cliffs, and even a shout comes back at you with a startling clarity.
The Quebrada de las Conchas, the Gorge of the Shells, takes its name from marine fossils found in the rock, a reminder that this was once a sea floor. The sandstone and clay were laid down in layers over many millions of years, and then folded, uplifted and carved by water and wind into fantastic shapes. The colours range from deep red through orange and pink to ochre and green, and they change with the light. Along the road, different formations have names such as the Toad, the Friars and the Obelisk, and the tourist buses stop at each.
The road, Route 68, runs along the Las Conchas river, which is a modest stream in the dry season but can rise to a torrent after rain. It is a quick, flowing ride, with long bends, few intersections and light traffic, though tourist buses and trucks stop and start unpredictably. Watch for sand and gravel on the corners, and for pedestrians at the main stops. Dust can be a nuisance in dry weather, and the sun is strong at this altitude, so sunglasses and sunscreen are important. The best light for photography is in the morning and late afternoon.
The valley is dry and warm, with temperatures in summer often above thirty degrees, and sudden storms in the afternoon. In winter, the days are mild and the nights cold. Rain, when it comes, can make the dirt tracks to the viewpoints slippery, and flash floods are a real danger in the dry river beds.
Cafayate, about thirty-eight kilometres away, is the nearest town with fuel, restaurants and wineries. There are some stalls near the Amphitheatre selling drinks, snacks and local crafts, but not much else. Pack water, and a small amount of cash for the musicians.