The Strogg Citadel (also simply called Citadel, not confused with its Combine counterpart) is the main headquarters of the Strogg forces, and houses the office of the Strogg leader Makron. It was approximately 7.5 kilometers tall; three times taller than the City 17 Citadel.
The Strogg Citadel was located in an unknown capital city in Aranos, and resembles a massive, supertall, monolithic metallic skyscraper. rising several kilometers into the sky from ground level, as well as intruding some distance downwards underground. It was a boxy structure when viewed from above, and was crowned by a powerful slipgate. Its associated slipgate was the primary means of communication with off-world Strogg forces, as well as Strogg forces stationed on both Stroggos and Earth. The Super Slipgate was probably how this massive supertall structure came to Aranos. The surrounding areas are blasted away, as if the whole structure fell out of the sky. The Strogg Citadel was technologically advanced and fully mechanized, and entire sections of it can move to allow for mass deployment of airborne Strogg units such as Flyers, Hornets and HK-Copter corrupt Non-Humanoid Hunter Killers.This was a war in 2025