The Boston Society of Architects has chosen the Isabella Stewart Gardner Museum's new wing as this year's "most beautiful building," despite that the addition designed by celebrated architect Renzo Piano opened nearly four years ago. If you're confused why the building is just now receiving the BSA's Harleston Parker Medal, we were, too, but apparently the award is given annually to a building built within the past 10 years. (The Harleston Parker Medal, established in 1921 by J. Harleston Parker in memory of his father, was first awarded by the BSA in 1923.) Since the Gardner addition opened, winners have included the MIT Media Lab designed by Fumihiko Maki (2012), Roger E. Wellington Elementary School designed by Jonathan Levi Architects with Burt Hill (2013), and the MFA's Art of the Americas Wing designed by Foster + Partners with CBT Architects (2014). "This is a thrilling moment in the history of the Museum," Steve Kidder, president of the Gardner's board of directors, said. "The new wing was first and foremost a preservation project to relieve the historic palace from some of the daily wear and tear of increased programing and amenities necessary in a 21st century museum. At the same time, we worked diligently to build a stunning and effective new wing that both respects and compliments Mrs. Gardner's vision."