Hearst Castle’s Neptune Pool is now the hottest place to take a dip along California’s Central Coast. Only it will require you to join The Foundation at Hearst Castle with a minimum donation, which helps fund the castle’s art conservation and education programs (and the minimum amount for a members-only swim event is $950). But can you really put a price on the opportunity to swim at this storied San Simeon landmark within the California State Parks system, built for newspaper publisher William Randolph Hearst between 1919 and 1947? Open for only five pool nights this summer and fall (July 6, August 4, August 24, September 21, and October 20), it’s a rare chance to float and frolic where famed stars like Howard Hughes, Joan Crawford, and Charlie Chaplin have. Admission is capped at 40 people, so lucky attendees aren’t elbowing one another for the privilege of swimming in one of America’s most iconic design attractions.

The exterior of Hearst Castle in San Simeon, California. Photo: Getty Images/Joe Sohm

The new form of fund-raising is a more casual way to bring in money, a shift from the traditional ball gown attire of fund-raisers of the past. Last October, the outdoor 104-foot-long Neptune Pool—designed by the castle’s overall architect Julia Morgan—reopened after a $10 million renovation. Four Italian-relief sculptures, Vermont marble, colonnades, and the Greco-Roman style (part of the original design) are a testament to both Hearst’s and the architect’s appreciation for their home state of California. Over Morgan’s lifetime (1872–1957), she designed approximately 700 buildings, with the Hearst Castle being her most well-known. She’s also celebrated as the first woman to be admitted to the L’Ecole nationale supérieure des Beaux-Arts’ architecture program in Paris (during the 1890s)—as well as being California’s first licensed female architect (in 1904).

The Neptune Pool at Hearst Castle, which features marble statues of Roman gods and goddesses. Photo: Getty Images/George Rose

The Roman Pool, which is the castle’s indoor pool, will feature it's own fund-raiser on October 20 for up to 20 people who have also made a minimum donation to the foundation. Built to mimic an ancient Roman bath, as Hearst requested, it’s a veritable sea of blue and orange, thanks to shimmery glass mosaic tiles inspired by the Mausoleum of Galla Placidia in Ravenna, Italy, and created by British muralist Camille Solon. The walls are all marble and the ceiling a faux evening sky with stars. Eight marble statues of Roman gods and goddesses (copies carved by Carlo Freter in Italy) are your view while you swim.

Reservations for all swim events opens on July 1.