- You may also be looking for Great Barrier Rift.
The Great Rift is an area of sparse star count between the Sagittarius and Orion Arms of the Milky Way Galaxy. Deep in the Alpha Quadrant, far beyond Federation space, it was largely unexplored by the until the late 2360s. The USS Marignano was assigned to survey the Great Rift in 2369.
Star systems and planets in the region include 22 Ophiuchi, 127 Scorpii, 334 Scorpii, 1440 Ophiuchi B V, 1616 Ophiuchi VI, 1865 Serpens, B Hydri, Beta Ophiuchi VI, and Chi Scorpii. UFC-7761, UFC-921-Alpha and Randolph's World are also in the Great Rift. (TNG novel: Intellivore; Star Trek: Pendragon: "Past Watchful Dragons", "Of Shadows and Starlight", "Another Time, Another Place")
The Lalairu frequently traveled through the Great Rift. In 2366, Starfleet Commander Hwiii ih'iie-uUlak!ha' joined the crew of a Lalairu vessel that ventured into the Rift, where he researched the structure of subspace hyperstrings far away from the more "crowded" space near the Federation. (TNG novel: Dark Mirror)
In 2356, Timothy Sinclair was also a passenger on a Lalairu vessel, and left them to explore the Rift on his own. He spent more than six months on his own and visited UFC-29 Persei VI, Randolph's World and UFC-7761 IV, where he found artifacts of ancient civilizations, including the Minbari. (Star Trek: Pendragon: "Past Watchful Dragons", "Whispers As Loud As Thunder", "Of Shadows and Starlight")