PX9-757 was a planet in the Milky Way galaxy, controlled by Apophis, which held a Stargate. The planet was discovered by the Tok'ra as a secret base where Apophis was building a new advanced mothership. A dense forest lied in front of the massive superstructure where the vessel was under construction. SG-1, under the influence of the Atanik armbands, was able to enter and exit the facility relatively unnoticed, enough that Apophis' experimental craft, and the area surrounding the craft, was destroyed. (SG1: "Upgrades")
Behind the scenes
Stargate SG-1: The DVD Collection issue 12 identifies one of the glyphs for this planet as the point of origin for Abydos. However, this could not be possible due to the fact that the point of origin appears only on that gate. In addition to this the address is only five glyphs long, when gate addresses need six.