clipped from: www.ubasics.com   
Countless children (and adults) have wondered where they would end up if they started digging straight down (ignoring the material and methods). Now we have the answer! Most of the planet is covered in water, so most diggers will dig into some ocean or another. What little land there is is generally not opposite other land. Some of South America and Asia, for instance, are opposite each other, but most Americans will swim in the Indian Ocean.

Drag the map and the other map will show you where you end up. If you double click somewhere on the map it'll zoom in to where you double-clicked.