London built an underground subway to transfer the mail in the 1920’s. Hidden from public view for decades, the “Mail Rail” dutifully shuttled snail mail until 2003, when its cost simply became too much.
Now, it’s coming back. Soon, parts of the defunct railway will be opened for tours, but not before they can be meticulously preserved with 3D laser scanning. The British Postal Museum & Archive (BPMA) has teamed up with ScanLab Projects to sweep the place with LIDAR (light detection and ranging) sensors.