Behold one of the Seven Wonders of the World! Machu Picchu is located in Peru and has an altitude of 7,970 ft above the sea level. The Inca tribe built their cities here in the late 14th century. No wheels were used to transport heavy rocks for the construction of the city. Also, the Incans used a technique called "ashlar" to build their cities. Stones were cut to fit together without mortar using this process. Surprisingly, not even a needle can fit in between two stones. Many of the stones used to build the city were over 50 tons so some were chiseled out from the granite bedrock of the mountain ridge. Other stones took hundreds of men to carry up the mountains. More than 600 terraces prevent the city from sliding down the mountain. It's incredible how these Incan ruins still remain here today!