The Siberian Research Facility, also named "Union Base," is a research facility in Siberia. Appropriately, it housed the Ice Replika.
It was first seen in "Cold Sweat," and last seen in "Down to Earth." In "Cold Sweat," X.A.N.A. sent William to this facility to prevent Yumi and Odd from destroying the supercomputer it housed. Aelita used the tower regulating this to get the programs controlling William. Aelita used the supercomputer here in Down to Earth to enter the data to help save William. This facility's supercomputer was never actually destroyed, as the skid was destroyed first. However, Jeremie's X.A.N.A. Destruction Program probably purged it. The facility also manufactured the Siberian Robots, a series of robots capable of combat, which X.A.N.A. would have used to take over the world. It also contained a room filled with brains in tanks.
Union Base's exact location is 63 degrees north, 16 minutes north, 143 degree 15 minutes east.
Disturbingly, there is an actual facility of some kind there, with the same general shape as the facility as shown in the show.