Does anyone have a 3D viewer of Boston with an underground component? During the Big Dig, it was rumored there was some sort of multi-dimensional CAD-ish mockup that allowed a user to see what was underground (tunnels, utilities, garages, etc) both on each lot and under the streets. Is this a unicorn or does this exist? Is there someone in the know? Possible applications would be figuring out what could go into Dewey Square (I know, not much), possible NSRL alternatives, or if the Silver lines could be sewn together with minimal obstruction.