The final part of the Peruvian adventure details a four-day mountain hike culminating in Machu Picchu, a site of Inca ruins. The experience is described as both a climax and an anti-climax due to the overwhelming crowds upon arrival. The author recommends the Classic 4 Days/3 Nights Inca Trail Hike with a local tour operator and reflects on the formation of strong friendships within the hiking group. The journey itself is highlighted, with challenges faced at high altitudes, and the beauty of the natural surroundings is deeply appreciated.