The Thames Tunnel was planned to link Rotherhithe and Shadwell but was abandoned halfway as costly and unsafe. It had a glass roof from which the river overhead was visible.
Rotherhithe Bridge was build above the river after construction was halted.
Fu Manchu used the tunnel as a base of operations, having built a poorhouse on its entrance to mask it.
Inspiration
The Thames Tunnel, now known as Rotherhithe Tunnel was the first underwater tunnel in the world although its name is not mentioned in the comic.