When things directly oppose each other, they're antipodal. Geographers use antipodal for places that are on the exact opposite sides of the earth from each other.
Parts of Spain are antipodal to New Zealand — in other words, if you drew a line straight through the center of the earth, you could connect those two countries. The Greek root of antipodal is antipous, "with feet opposite ours." You can also use this adjective figuratively to mean "opposed." If you and your brother couldn't be more different (you like vanilla, he prefers chocolate; you're a dog person, he loves cats), the two of you are antipodal.