If you zoom in, you can see it's not a single structure or building. Most of the area (all the blue parts) is some kind of liquid, probably water. Zoom in far e

If you zoom in, you can see it's not a single structure or building. Most of the area (all the blue parts) is some kind of liquid, probably water. Zoom in far enough and you can see buildings on the edges of the pools. Follow the little blue line upwards from the structure and you'll see a dam clearly pumping water, and the canals extend up to around 50km. The Map View also shows a large area around it as a huge lake, so I'm guessing they drained the lake. Still pretty impressive in my opinion.