Starbase 257 was a Federation space station that was in service with Starfleet in the late 24th century. While within its defense perimeter, ships had to remain at one-half impulse.
In 2374, the starbase was attacked by a wing of Jem'Hadar fighters, shortly after the runabout USS Shenandoah had left the station en route to Ferenginar. (DS9: "Valiant")
For more information on the model used for this design, please see studio models.