This colony was only mentioned in dialogue.
In the original script, the colony was called "Prophet's Haven"'. (Star Trek: Deep Space Nine Companion - A Series Guide and Script Library)
According to Startrek.com, Star Trek: Star Charts (p. 46), and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), this colony was located in the Alpha Quadrant. The colony orbited a K-class star.