Most commonly reached via travel from Cusco, Ollantaytambo is an Incan archaeological site in the Sacred Valley of southern Peru. The town dates from the late 15th century and is home to some of the oldest continuously-occupied dwellings in South America. Its primary attraction is the fortress ruins, and it's also a favorite starting point for the famous Inca Trail, a four-day, three-night hike to Machu Picchu.