It was located on a "shadow nebula" of approximately a 10-12 lightyear span. In the year 2267, the Federation starship USS Enterprise was on course for Starbase 200 after surveying a planet, but diverted twice when it detected momentary distortions in the spacetime continuum. (TOS episode: "The Alternative Factor") Due to a series of system failures (including life support and reactor), the starbase was abandoned in 2305. (Last Unicorn RPG module: All Our Yesterdays: The Time Travel Sourcebook)