For the curious who have wondered just what the giant red crane next to Berkman Plaza II is for, here’s your answer: The massive mobile unit now situated on Bay Street is being used to take down the large tower crane that’s affixed to the under-construction residential building, said Stephen Gaedchens, a service manager for the company that operates the crane. The job is being completed by 10 workers, he said, and should take several days, weather permitting.