P3X-439
The monument of P3X-439
Astrographical information
Galaxy	Milky Way
Societal information
Race	None
Technological period	None, formerly advanced
Earth interest	Ancients' repository of knowledge
Under control of	None, formerly Ancients
Out of universe information
Appearances	"Lost City, Part 1"

[Source]

P3X-439 was a planet in the Milky Way galaxy once home to an Ancient colony. Less than a kilometer from the Stargate, a team from Stargate Command found an enormous (and headless, due to its age) colonnade containing a Repository of knowledge at the base.

The Goa'uld Anubis sent a reconnaissance probe 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 Death Gliders and Al'kesh, SG-1 destroyed the repository after Colonel Jack O'Neill took the drastic step of interfacing with the device. (SG1: "Lost City, Part 1")

SpeculationEdit

The monument, to some, looks oddly like an Ancient Control chair, which leads some to wonder whether this is where the first Control chairs were made (and possibly many of the things that go with them).