The Great Wall of China is one of the world's greatest engineering marvels, and it took dangerous, cutting-edge construction to build it. Experts use the latest tech and modern-day science to reveal if building it a second time would be as deadly.

Venice, Italy is a city in crisis, and it took dangerous, cutting-edge engineering to build it. As apocalyptic floodwaters unleash havoc, experts use the latest tech and modern-day science to reveal if building it a second time would be just as deadly.