Boston real estate agent and condo expert David Bates reviewed the 50 most expensive (per square foot) Boston condominiums in 2017, and found five key amenities they had in common:

• Many are in Millennium Tower. Twenty-eight condominiums on the list were located in this distinctive building.
• They’re large in square footage. The average size of a Boston condo that sold in 2017 was around 1,000 square feet, but the average size of a condo on this elite list topped 2,700 square feet.
• They’re in exclusive neighborhoods. Only Back Bay, Beacon Hill, Waterfront and Seaport produced sales that made the list.
• Most buildings had a concierge or a doorman. Some had both.
• Condos in small, historic buildings can still command a premium. There are buyers who desire condominium homes that are unmistakably Boston – that exude its history, are often warmed by a red brick façade and provide intimacy and privacy in a location that is protected from development.