Head for Machu Picchu this morning (just about 8,000 ft. above sea level), stopping first at the town and archaeological site of Ollantaytambo, and its ruins of an Incan fortress containing a maze of narrow cobblestone streets, adobe houses, aqueducts, and the remains of a stone temple, the best example of Incan urban design in existence. Then board a scenic train ride to Aguas Calientes. The village is a former railroad camp in a gorge surrounded by cliffs and cloud forests, the closest access point to the mountaintop ruins. From here, you'll ride up a winding mountain road of hairpin turns to reach the "lost citadel," steeped in legend and mystery. Its purpose and original name are unknown; when Hiram Bingham discovered it in 1911, he followed the directions he was given to the place beside the Old Mountain (Machu Picchu), which was the name he gave it. Guided by a local expert, tour this mystical complex of giant walls, stone terraces, steps, ramps, and astronomically aligned structures, described by UNESCO as "the most amazing urban creation of the Inca Empire at its height," surrounded by breathtaking mountain landscapes. After the guided tour, enjoy free time to explore on your own.