Pomplance was a neutral planet within reach of the Federation, Klingon Empire and Romulan Star Empire in the galaxy's Alpha or Beta Quadrant.
History and specifics
Pomplance was known as a pleasant world which yielded vintages of wine. The Pomplancian Bureau of Interstellar Affairs maintained an off-planet mission on the surface for outworlders.
In 2269, James T. Kirk and Spock met with Klingon and Romulan representatives on Pomplance to settle a mining rights dispute for the WWB7 system, but negotiations halted after delegates were dosed with a truth serum. (TOS audiobook: In Vino Veritas)