On the approach to OLLANTAYTAMBO from Urubamba, the river runs smoothly between a series of fine Inca terraces that gradually diminish in size as the slopes get steeper and more rocky. Just before the town, the rail tracks reappear and the road climbs a small hill into the ancient plaza. Built as an Inca administrative centre rather than a town, it’s hard not to be impressed by the foundations that abound in the backstreets radiating up from the plaza, especially in Calle Medio. Laid out in the form of a maize corn cob – and one of the few surviving examples of an Inca grid system – the plan can be seen from vantage points high above it, especially from the hill opposite the fortress. An incredibly fertile sector of the Urubamba valley, at 2800m above sea-level and with temperatures of 11-23°C, with good alluvial soils and water resources, it was also the gateway to the Antisuyo (the Amazon corner of the Inca Empire) and a centre for tribute gathering from the surrounding valleys. Beyond Ollantaytambo, the Sacred Valley becomes a subtropical, raging river course, surrounded by towering mountains and dominated by the snowcapped peak of Salcantay.