Zebras. None of Twilight's friends had even known they existed before seeing Zecora. But zebras exist, and are sorely absent in Equestrian society. Seeing a gap to bridge, Twilight decides to head to Zebrabwe, the zebra homeland, as an ambassador and open diplomatic relations. New friends are new friends, no matter where they are.
But things aren't all as they seem; Equestria isn't the only country interested in Zebrabwe, and definitely not the closest. Zebrabwe has neighbors of its own, and there's a reason zebras in Equestria are harder to find than needles in haystacks.
AUTHOR'S NOTE: "Zebrabwe" was originally "Gondwana" before I decided that the country needed a horse-pun name. Early comments mention Gondwana rather than Zebrabwe.