Megastructures

From the Great Pyramid at Giza to the towering skyscrapers of today, humans have engineered massive constructions for at least 5,000 years. But why? How do biology and human emotions affect our desire to build gigantic structures? Why were the earliest mega-structures almost always pyramids? Why do people have the urge to build tall, and how do mega-structures on earth echo a basic principle embedded in the very structure of the universe?