Stargate Atlantis
The main subject of the seventh season of Stargate SG-1 was researching and locating the city of the Ancients. At the end of the seventh season, SG-1 discovered that the city is on Earth, under the ices of Antarctica. But it was in fact only a beachhead. Doctor Daniel Jackson finds the coordinates of the real city. Its name is Atlantis (the legendary ancient city), and it's in the Pegasus galaxy. The address was hard to find because it needs eight chevrons, the seventh of which is used to indicate the galaxy.