A team of scientists has discovered an amazingly complex subterranean city built by millions of Leaf Cutter ants in Brazil. Now abandoned, the once thriving insect metropolis features a vast network of underground tunnels, covering an area of 500 sq ft and extending 26 ft below the surface. The researchers pumped in more than 11 tons of concrete to reveal the giant labyrinthine structure. More info, including video, at Mail Online.