In 1990, two thieves dressed as Boston police officers told the museum night guards on duty that they were responding to a call. The thieves passed the sole security door. There was just one alarm button at the time; only motion detectors traced their movements. There were no cameras. A mere 81 minutes later, they were in possession of the masterpieces worth, today, half a billion dollars. The investigation is ongoing. 

The new building could have been a fortress. But that would have made the theft the focal point of how we would perceive the museum. Instead, the colorless glass entry, the brick walls, even the enclosed corridor that passes from the new building through a grove of trees into Gardner’s historic courtyard serve as practical access controls. There are no doors for the public to the original Gardner mansion. A thief would now have to walk through a transparent glass tunnel, into the new building, and out a security door for the easiest exit. Though counterintuitive, its openness makes it more secure. 

While the museum is watched by hundreds of cameras, the new structure is designed to relieve some of the stress from Gardner’s old home by shifting the burdens of exit and entry to the much more modern and secure building. “There is simply no place in the museum where a thief can just grab art and get outside,’’ Anthony Amore, the head of museum security and author of “Stealing Rembrandts,’’ said.