Even though Runkuracay was the smallest of the ruins that we saw along the Inca Trail, they are the ones I remember the best (except for Machu Picchu, of course).
Runkuracay stuck in my memory because of its spectacular location and perfectly circular shape. This site is a true testimony to how amazingly advanced and rich the Inca civilization was at its prime. It seems like there was no task too difficult for them: they could build anything they wanted, anywhere they wanted. It’s even more admirable if you take into account that they did not use mortar, and that despite that, many structures survived in a pretty good shape till this day.
It’s unknown what the purpose of Runkuracay ruins was but, as it occupies a commanding position overlooking the Pacamayo Valley below, it’s likely that it served as a lookout point.