About 2-3 hours and 2000 feet of elevation gain after you begin your trek at Km104 you turn a corner and Wiñay Wayna comes into view. This Inca site was discovered by the Wenner Gren Scientific Expedition to Hispanic America, which investigated both archaeological sites and native Andean peoples in 1940-42. The ruins are huge. You can see the tiny hikers if you look in the lower left of the image.
The site's lookout nature, it's positioning near the important Inca access road, and the investment represented by it's architecture suggests it was a place of some importance during the Inca occupation of this segment of the Urubamba drainage. Anytime except the rainy season of November to March is a good time to hike the Inca Trail. This shot was taken in late September.