During World War II, the Thorp building on Central Avenue was considered one of the most secret and best-guarded buildings in the country.

The building was used to manufacture the Norden Bombsight, a device that allowed pilots to drop bombs more accurately.

"They wanted to make sure this secret was protected," Randal Dietrich, with the Minnesota Military Museum and Library said. "I believe the U.S. military identifies this innovation as a game-changer. This is important. Certainly, armed guards and security personnel and protocols are in place, who passes in and out is closely monitored."

The production of this secret weapon was so important to the Allied war effort that the FBI and U.S. Navy closely guarded the building around the clock during the war.

The Thorp building is now used as a creative mixed-use center, focusing on the arts. It's even home to a craft distillery and cocktail room.