El Anfiteatro comes next — a natural amphitheatre hollowed from the canyon wall, a circular space perhaps 70 metres across, its curved red walls rising steeply on all sides. The acoustics are the thing: a handclap produces a long, rolling echo, and it is common to find a musician stationed at the centre, the sound of a quena or guitar filling the space in a way that justifies the detour entirely. Walk to the centre and make some noise.