A River Flowing Through the Heart of Tokyo Was Dug by Hand

The 500-meter wide river that runs through Tokyo is actually an artificial canal dug by humans. After Tokyo's east side was completely submerged by a great flood in the 1910s, they decided to create an additional channel for water drainage. It's 22 kilometers long. The project was led by an engineer who was the only Japanese person to participate in the Panama Canal construction. It took 20 years of digging with shovels and pickaxes, involving a total of 3.1 million person-days. Even though they experienced the Great Kanto Earthquake midway, the floodgates he built reportedly remained intact.