Opened in 1940 to accommodate the Combined War Headquarters of all three services underground to protect it from aerial attack, this complex housed the Fighter Sector Operations Room used during the Battle for Malta 1940-43 along with other operation rooms and ancillary facilities. After the end of the war it was used by NATO up to 1977 to track the movement of Soviet subs in the Mediterranean.

Exclusive guided tours are offered twice daily one at 10.30 and another one at 13.00. The fee for this tour is €15.00 per person which also includes a tour of the Saluting Battery.

Tickets are available online.