Cestus III
Cestus III is a Class M planet of the Cestus system, located in a region bordering the territory of the Federation and Gorn Hegemony, near the Metron Consortium. It was considered to be "on the other side of the Federation" from Deep Space 9. (TOS: "Arena"; DS9: "Family Business")
In the late 23rd century, Cestus III was on the frontier of Federation space, beyond which little was known. A small Earth Observation Outpost and colony was established, commanded by Commodore Travers. The establishment of this foothold alarmed the Gorn Hegemony; they regarded Cestus as part of their space and the colonists as invaders.
In 2267, a Gorn captain led his starship and ground forces in a counter-invasion strike, destroying the colony and slaughtering most of the colonists. Using faked communication and impersonating Travers, the Gorn lured the USS Enterprise to Cestus III, where the landing party, led by Captain James T. Kirk, beamed down to the planet's surface. The surface forces were repelled, and the Enterprise pursued the Gorn vessel to a point near 2466 PM, where both ships were seized by the Metrons and their captains forced to do battle. (TOS: "Arena")
Kirk's confrontation with the Gorn on the planet would later become one of the most famous incidents in his career. Benjamin Sisko once admitted he'd like to shake Kirk's hand and "ask him about fighting the Gorn on Cestus III". (DS9: "Trials and Tribble-ations")
By the 24th century, the dispute with the Gorn was resolved and the Federation re-colonized the planet. In this era, Cestus III is approximately two weeks from the Bajoran system by subspace message and eight weeks at the Xhosa's maximum warp. In 2371, the colonists formed a baseball league with six teams, including the Cestus Comets and the Pike City Pioneers. Kasidy Yates's brother lived on Cestus III and invited Sisko and his sister to see a live baseball game at the colony. (DS9: "Family Business", "The Way of the Warrior")