Online toy

This Map Tunnelling Tool is very interesting. Want to dig a tunnel through to China? You need to start in Argentina. Or underwater.

What's really interesting is how much of the surface of the earth is covered by water. It's one of those things that you intellectually know, but you don't necessarily realize or visualize from a globe or a map. But almost anywhere on land that you start, if you go straight through, you're coming up in the ocean...