From World War 2 until the 1990s, Walter Reed owned and used the National Park Seminary girl's school buildings at Forest Glen, MD. They didn't maintain the buildings well; around 1989 or so I rescued a post-Works Project Administration mural of the Seminary by Jack McMillan which showed orange jumpsuited psychiatric patients on the grounds. It was being damaged by water leaking down from 3 floors above. The painting is restored and on display in the Museum; in the meantime, you can take tours of the buildings as explained in this article "At an Old Retreat, Signs of Renewal," by Amy Orndorff, Washington Post Friday, April 25, 2008; Page WE05 (which is not quite factual - the theater burned down). There's two photographs on the site as well.
A few points of interest - the fountain, which was badly damaged the last time I saw it, was a sixteenth century work imported from Italy if I remember correctly. Also the ballroom in the main building was restored and is stunning, although a lot of the busts that lined it are missing.
The place is well worth seeing. It's being turned into condos now.