The drainage infrastructure constructed by the Inca at ancient Machu Picchu represents a significant public works achievement. The difficult site constraints associated with the nearly 2,000 mm per year of rainfall, steep slopes, landslides, and inaccessibility posed drainage challenges that were met successfully by the Inca. The technical analysis of the Inca drainage works demonstrates that the drainage criteria used were reasonable and the implementation exceptional, and that the Inca were good engineers even though they labored without the benefit of a written language or the use of a wheel. Proof of the Inca success with drainage rests with the fact that Machu Picchu lay in the rainforest for 400 years without failure. There is no better example of successful ancient civil engineering than Machu Picchu. It was built by Native Americans before the arrival of the Spanish Conquistadors, was essentially abandoned in 1540 A.D., and endured for 4 1/2 centuries under a thick rainforest until the 20th century. Scientists, engineers, and laymen alike continue to marvel at the wonders of Machu Picchu.