World that was once home to an Ancient colony. Less than a kilometer from the Stargate a team from the S.G.C. found an enormous (and headless, due to its age) colonnade containing a repository of the Ancients' knowledge.
The Goa'uld Anubis sent a reconnaissance drone to the planet to scout, which discovered the secrets the planet held. SG-1, SG-3 and SG-5 arrived first, narrowly missing the arrival of Anubis's fleet. Flanked by gliders and Al'kesh, SG-1 destroyed the repository after Jack O'Neill took the drastic step of interfacing with the device.
HOME TO - Unknown
FIRST APPEARED - Lost City, Part 1
Lost City, Part 1 - S.G. teams travel to P3X-439 just before Goa'uld ships start entering the atmosphere.