Five-sided building which is the headquarters of the United States Department of Defense.
Located in Arlington, Virginia, just outside Washington, DC, the Pentagon famously has 17.5 miles of corridors. Maxwell Smart recalls a CONTROL agent who was so confused he was lost inside for three days. (It turned out that the agent was himself.) [Episode #22: "Smart the Assassin" and Movie: "The Nude Bomb".]
The Pentagon has been targeted for destruction by KAOS [Episode #16: "Double Agent"] but they have never succeeded. Indeed, when Siegfried commandeers one of Albert Pfister's "kamikaze" pigeons for the purpose it ends up destroying KAOS's own headquarters instead! [Episode #82: "Spy, Spy, Birdie".]
Nurseryman Algernon De Grasse, however, does get one of his bugged plants into the Pentagon's War Room before his scheme is discovered [Episode #135: "What's It All About, Algie?"] and the scientist called "The Brain" was able to sabotage its computer system during his lunch break [GS95 Episode #3: "Goodbye Ms. Chip"].