MASSACHUSETTS Boston The 149-room Mandarin Oriental, Boston will open in late 2007 adjacent to the Prudential Center. It will feature a spa and will be the location of Mandarian Oriental's second Residences development.WASHINGTON D.C. The National Portrait Gallery and Smithsonian American Art Museum will reopen after an extensive renovation on July 4, 2006. George Washington's Mount Vernon Estate and Gardens has begun construction on two new state-of-the-art buildings that are expected to open by late 2006. The Ford Orientation Center will introduce visitors to the personality and character of G.W. with a large-format, Hollywood-style 15-minute film. The Donald W. Reynolds Museum and Education Center will feature 23 galleries and theater experiences that will stress the importance of Washington's military and presidential careers. Marriott International and Gould Properties are developing a 1,200- to 1,500-room headquarters hotel for the new Washington Convention Center; it is slated to open in 2006 or 2007.TagsHotels and Resorts