This video is called "SimCity TrackMania City". It could also be called "SimCity Rollercoaster Tycoon City".
YouTube user MiguelM12345 says he "wanted to fill the water space with hand-drawed roads". And this is what happened.
I'm not so shocked that it happened. I'm more shocked it stuck, that the game's engine can handle it, and seems to actually work. Well. Except for the plane.