Star Trek: Deep Space Nine
Following the end of the occupation of Bajor by the Cardassians, the Federation reaches an agreement with the provisional Bajoran government whereby Starfleet is allowed to use an abandoned mining station as a local base of operations. Shortly after their arrival, the station's new crew discover a stable wormhole in the Bajoran star system, and move the station to its opening in order to claim it.
The first two seasons of the show dealt mainly with the aftermath of the occupation of Bajor, the reconstruction of the planet's political and social systems, and the early exploration of the distant Gamma Quadrant to which the wormhole lead.
From the third season onwards, the tone of the show shifted dramatically. The Dominion, an alien civilization sporadically mentioned in earlier episodes, was revealed as a major threat intent on conquering the Alpha Quadrant. The Dominion War dominated the later seasons, leading to some of Trek's darkest and morally most ambiguous episodes.
Fan reaction was generally positive, in no small part thanks to the show's intelligent writing which stood in stark contrast to the of the contemporary Star Trek: Voyager series.