sound installations, and both indoor and outdoor sculptures, totaling $1.4 billion in assets. The collection contains only works by artists who have already exhibited for at least 15 years. As a private art museum, Glenstone has been compared to the Frick Collection and The Phillips Collection. Many of the museum's large galleries feature only one or two pieces, do not contain explanatory text, and are sparsely furnished. While some exhibitions are permanent, the collection rotates through the galleries over time. Pieces from the collection are also loaned to public institutions both domestically and internationally. Glenstone limits entry to about 450 visitors per day. According to Rales, the limit is imposed to "give lots of space to our visitors, to really give them the time to explore and enjoy". Rales wrote that she used a formula to calculate the optimal number of visitors for the museum's size. The museum's staff is made up of recent university graduates, including some in postgraduate programs, through its Emerging Professionals Program, a two-year program for aspiring curators. Staff members are stationed in the galleries to answer questions from visitors about the art. Phone and camera use is prohibited in the galleries. In 2018, the introduction of the Pavilions expansion debuted single-artist installations and exhibitions from artists Cy Twombly, Robert Gober, Pipilotti Rist, Charles Ray, On Kawara, Martin Puryear, Michael Heizer, Lygia Pape, Brice Marden. Other artists who have been on display at Glenstone have included Roni Horn, Alexander Calder, Ruth Asawa, David Hammons, Alighiero Boetti, Kerry James Marshall, Shirin Neshat, Rirkrit Tiravanija, and Mark Rothko. Architecture Glenstone is noted for its peaceful natural setting, consisting of a cluster of galleries and other buildings set in a large wooded campus. The museum buildings are located toward the center of the campus, and visitors approach the galleries from gravel parking lots via a pathway through the property that is about long. In designing the campus, Glenstone's founders tried to establish a tranquil experience, leading them and art critics to refer to the museum as part of the "slow art" movement. Buildings The original Glenstone building opened in 2006 and was designed by American architect Charles Gwathmey of Gwathmey Siegel & Associates Architects. The building is a modernist limestone structure with of gallery space, located on of land. The 2018 expansion added of gallery space in a museum structure called the Pavilions, designed by American architect Thomas Phifer.