New York, your timing couldn't be better.

(not actually my photo)

"Hardly anyone knows that a secret tunnel runs deep beneath the Atlantic Ocean. In May 2008, more than a century after it was begun, the tunnel has finally been completed. An extraordinary optical device called a Telectroscope has been installed at both ends which miraculously allows people to see right through the Earth from London to New York
and vice versa."

This is probably the most insane thing I have ever seen. One end of the tunnel comes out near the Brooklyn Bridge, the other by the Tower Bridge, London. It seems stupid if you think of it as a giant public webcam, but the awe comes back when you realize that it is a physical tunnel through the earth's crust and that the image is carried using mirrors. Apparently it only goes until June 15... what will they do with it afterwards? Fill it in?

more info here and here