The two ends of the device sit by the riverside in both cities
Messages written to each side were rarely profound
Is there a very very long tunnel running between London and New York?
That is what installation artist and inventor, Paul St George, says he believes.
Over the coming weeks, thousands of people in both cities will get the chance to see if they believe him.
The ends of what Mr St George says is a giant telescope-like invention are currently poking out of the banks of the Thames in London and the East River in New York.
Stare into either end, and you'll be able to watch people on the other side of the Atlantic looking straight back at you.
The BBC's New York correspondent, Matthew Price, took a look.
First broadcast 23 May 2008