Drill straight through the center of the Earth from Mexico City, Mexico and you'd surface on the exact opposite side of the planet — its antipode.
Mexico City's antipode sits at 19.43°S, 80.87°E, in the southern hemisphere, east of Greenwich. That places it in or near the Indian Ocean.
It lies roughly 20,015 km from Mexico City — 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 Mexico City.
Like the vast majority of inhabited places, Mexico City's antipode falls over open water rather than land — water covers about 71% of the globe, and antipodal land pairs are rare. The nearest coastline, island or settlement is what Antigea shows you when you open the live map, along with the satellite view, the closest Street View, and the local time on the other side of the world.