Related Beal, the developer of The Clarendon, has announced the luxury condo development is now 100% sold with the sale of a $6.2m penthouse. The 33-story ultra modern luxury condo development at 400 Stuart Street has 103 luxury condos and is one of the most sought after buildings in the Back Bay. The Clarendon condos went on the market in 2010 and were released in phases. The building also has a rental development "One Back Bay" and has a separate entrance, and features luxury apartments for rent from the 4th to 13th floors.