The Alfred E. Clarke Mansion, also known as Caselli Mansion, Nobby Clarke's Castle and Nobby Clarke's Folly, is a building in San Francisco, California, located at 250 Douglass Street in the Castro neighborhood. Because Victorian mansions were predominantly built on Nob Hill, rather than the boonies of Eureka Valley (now the Castro), the building survived the 1906 San Francisco Earthquake and subsequent fires and, consequently, outlived most of its architectural contemporaries.