When the British Ministry of Defense built a nuclear bunker in the English town of Chilmark in 1985, it was supposed to act as a government safe house in the event of a nuclear attack. But when the Cold War ended, it no longer had an official purpose—that is until a couple of men snuck in and allegedly transformed it into a giant marijuana grow house.British police had suspicions about the fortress, which cops described as "almost completely impenetrable," and staked it out before raiding it on Wednesday. Once the officers got past the nuclear blast doors to the underground lair, they uncovered 20 rooms—each 200 by 70 feet—brimming with thousands of weed plants.Wiltshire police detective inspector Paul Franklin told BBC News that it was one of the largest crops the force had ever seen, with a street value of about $1.25 million. Shortly after the discovery, cops arrested six men between the ages of 15 and 45 and charged them on suspicion of cannabis production and human-trafficking offenses.The decommissioned fortified establishment is far from the strangest grow factory British police have stumbled on this month. Earlier in February, they uncovered a bunch of weed in an abandoned building at the Legoland theme park in Windsor—which was reportedly only accessible through land that's owned by the Queen of England.