The G5 Corporation's main building is situated in the backstreets of Chicago. It is fitted with a very sensitive alarm system along with a massive security force both inside and out. The level G5 Building: Reconnaissance is played here.
Not much else is known about the G5 Corporation or the building as it was only shown once throughout the game. It was however the meeting place of Cassandra De Vries, Trent Easton, and Mr. Blonde, and housed a copy of Dr. Carolls personality.