By the end of World War II, O'ahu was probably the most heavily armed island in the world. One of the many large gun facilities on the island was a maze of underground tunnels called Battery 405. Located on the Windward side of the O'ahu, its 2 8-inch guns faced the north and the east. After the bombing of Pearl Harbor the Territory of Hawaii did not see any war action but the battery was manned until the end of the war with its two cleverly disguised 8 inch guns kept ready for duty. After the war battery 405 was disarmed and from 1950-1992 the underground tunnels were used as a mushroom farm! Almost 7 decades after WWII, the tunnels are being restored, decades of grime sandblasted off the walls and soon battery 405 will serve as a secure site for archives of digital data and computer backups.