Originally controlled by the System Lord Morrigan, planet P3X-289 was under Goa'uld oppression until, for unknown reasons, it ceased to be (possibly an uprising as the Stargate was buried). The people were allowed to develop and progress in their own direction. Eventually the inhabitants dug up the remains of what they referred to as the Gate of Mahg Mar, located within the ruins of Danaan (possibly a central place of worship for Morrigan). The gate was put on display in the planet's Museum of National History.
The culture became technologically advanced and furthered in their studies of science until a cataclysmic event made the entire world uninhabitable. The people quickly devised a solution to save a handful of lives: an artificial containment dome, pristine in it's simplicity above-ground, but regulated by an advanced piece of machinery below. Once inside, their world crumbled beyond the barrier, but their technology continued to advance until they developed a vast super-computer known as The Link, capable of integrating the entire population into one enormous database.
After some 400 years the dome was failing, and SG-1 managed to save the people from the control of the Link. The inhabitants were relocated them to another planet. P3X-289 was abandoned, its entire environment poisoned and the dome doomed to fail in a matter of weeks or months.
Revisions - SG-1 travels to P3X-289 where an entire civilization has been destroyed, leaving behind a few thousand survivors who are interconnected via a subterranean super-computer.