Digging a Hole

This instillation by Berlin-based firm Topotek1 is brilliant. They created these holes in different parts of the world each hole has a audio link so that if your standing at the hole in Argentina you are listening to the traffic from New York. It's suppose to be a connection to that childhood activity when you wanted to dig your way to china. I think the audio adds a great touch to the project don't you think? What i wonder is how far do those hole actually go down. 

Images via Colossal