What Are the Chinese Building Underground in Hainan? A satellite captures an image that uncovers the entrance to an underground complex. What is being built there? Facebook Prev Article Next Article Engineering Checkout these cool gadgets... Related Posts Is Sundrop Farms the Future of Agriculture? Super Fast Cameras (1 trillion FPS) 3D Printed Objects that are Otherwise “Unmanufacturable” Ion Propulsion – The Plane With No Moving Parts The World’s Longest Underwater Tunnel Testing Which Battery Lasts the Longest