The principal setting of the series is the Starfleet-controlled space station Deep Space Nine, located adjacent to the mouth of a stable wormhole near the planet Bajor. The Bajoran wormhole provides instantaneous travel to the Gamma Quadrant, a region on the other side of the galaxy. During the second season of "Deep Space Nine", the Dominion, a powerful empire in the Gamma Quadrant, is introduced; and over the course of the second and third seasons, more information about the Dominion is revealed. Conflict escalates through the fourth and fifth seasons, as the Dominion infiltrates Alpha Quadrant powers and eventually forms an alliance with Cardassia; open warfare begins at the end of the fifth season, when the Dominion briefly occupies Deep Space Nine, and continues until the Dominion is finally defeated in the series finale.