The StarGate Inc. Cross-Dimension Base (Or just the SGI Base) is StarGate Inc.'s main base. It contains portals to key locations, like The Portal Towers, and is undetectable by most (usually all) technology. Exceptions include SGI-related technology, space stations (due to having a vantage point, and a hole in the masking shield), and a branch of the American government dedicated to helping SGI stop people from doing stupid things.
The Base was located in what would be the Bermuda Triangle. As of Legend of Ender 40: Double Mobius (a Homestuck crossover), the base is located on SBURB Epsilon's newly created planet, Epsilon (no surprise there).