Approximately eight kilometers away from the town of Terni in Umbria, Italy, there is a waterfall that is one of the highest waterfalls in Europe: Cascata delle Marmore or the Marmore's Falls.In reality, this waterfall is not natural. The waterfall is the world's tallest man-made waterfall, standing 541 feet tall (165 meters). Its towering presence is a 2,000-year-old testament to human engineering.Romans created in 271 BC the former hydraulic system and the shape of the waterfall. During the Roman era, the River Velino had become vastly enlarged and had created a vast swathe of swamp-like, stagnant water. This unhealthy wetland...