Drill straight through the center of the Earth from Boston, USA and you'd surface on the exact opposite side of the planet — its antipode.
Boston's antipode sits at 42.36°S, 108.94°E, in the southern hemisphere, east of Greenwich. That places it in or near the Indian Ocean.
It lies roughly 20,015 km from Boston — about as far apart as two points on Earth can possibly be. And the relationship is symmetric: the antipode of that spot is, of course, right back here in Boston.
Boston's antipode falls over open water, in or near the Indian Ocean — water covers about 71% of the globe, so antipodal land pairs are rare. The nearest named place is Cow and Calf Rocks, a small island in Australia, roughly 1,031 km away.
Antigea's live map shows the satellite view, the closest Street View, and the local time on the other side of the world.