Quoting selectively from the introduction to this video:
Ollantaytambo, probably one of the most visually perplexing sites within Peru.
Claimed to be that of the Incas, and at an altitude of 2,792 metres above sea level, once one takes a good look at this place, it becomes near impossible to believe that the Incan civilisation, with their access to such limited technologies, could have created such a place.
The main settlement at Ollantaytambo has an orthogonal layout, with four longitudinal streets crossed by seven parallel streets. At the centre of this grid, is a large plaza that was open to the east and surrounded by halls, and other town blocks on its other three sides. Buildings in the northern half are more varied in design. Interestingly, the amount of erosion that has occurred over the years, has rendered the original plans is hard to establish, perhaps a clue to its true age?
Content Source: Mystery History