The ACF headquarters is a massive building complex floating in international waters, is the center of operations for the foundation, home to high class personnel, and prison to a few select anomalies.
The headquarters themselves do not look particularly interesting, most of its many edifices are simple rectangular concrete blocks— with seldom few windows along their outer surfaces. The foundation's logo and initials are stenciled over their façades— just in case anyone working within could forget where they were. What makes the ACF HQ stand out, however, is how it remains on the water. Rather than being attached directly to the seafloor beneath it, the ACF headquarters instead floats on the top of the ocean via a state-of-the-art, giant, inflatable sunshine-yellow duck innertube.
Don't laugh, it was cheaper this way.