Obelisk of Ancient design. The Ancient text on the outside defines the object as an aperture, or gateway, to "enlightenment." In reality the device sends an individual kilometers across the serface of the planet, bypassing the Mountains of Dor Tanak, to the Sodan village on the opposite side.
What is not known is whether or not the device itself is responsible for initializing a personal gateway, though Colonel Carter did detect an energy signature within the column of stone. It is also not known how the device itself functions. Whether there must be an identical column on the receiving end, or whether there are countless obelisks scattered across the planet (or others, bidding interplanetary access throughout the galaxy) is not known.
KEY EPISODE(S) -
Babylon - SG-22 locates an Ancient transporter, the device responsible for allowing the Sodan to flee into safety so quickly.
Arthur's Mantle - A transformed Volnek steals a crystal from the Sodan side of an their Ancient transporter, preventing anyone from using it to escape the area.
