This is the Swann Memorial Fountain, constructed in 1928 to honor William Carey Swann, founder of the Philadelphia Fountain Society. I don't know if I am more impressed with the fact that there is a fountain society, or that its founder has the perfect name for a fountain.
Nicolle attended a Dîner en Blanc event at this fountain last year. The event, which started in Paris twenty-five years ago, is mostly spontaneous. All attendees wear white and bring their own dinner. Nicolle writes that it was a wondrous experience to dine in a "sea of white." Indeed, browsing the photos in the gallery on the link above made me smile and wish for a Dîner en Violet. I'm a bit too old for white :)