The Inca Trail (at least this one) is the famous trail that leads to Machu Picchu in the Andes in Peru. Some of it is original, but of course there has been maintenance over the years. I went in a relatively slow time of the year, so there were only hundreds of other people on the trail. Soon after, a permit system was instituted to control crowds.
The trip takes four days, crosses a number of high passes. It starts in relatively arid terrain, and moves into rainforest as you get closer to the end. All but the last night are spent in tents, and you are required to hire one of the local guiding companies. You cannot just head out on your own. The basic package does not include carrying your gear, but you can pay extra for a donkey to carry your pack if you want to.
You start by taking the train from Cuzco to the starting point, and pass many smaller ruins during the hike. I carried my own pack, and some of the passes were quite high.