Upcoming: 33

Glenstone, a private art museum in Potomac, Md., looks forward to a $125 million expansion. Come 2016, a new series of exhibition spaces will be open five days a week, albeit by reservation only. Important works by mid-century moderns (Serra, Pollack, Johns, de Kooning) and contemporary artists are part of the collection of Mitchell and Emily Rales. Carol Vogel has the full story.