The Neptune Pool is the name of the outdoor swimming pool ensemble at Hearst Castle, in San Simeon, California. Featuring the significant swimming pool, it also includes: fountains, ornamental pools, sculptures, marble pavilions, alabaster lanterns, dressing rooms, and an ancient temple facade (mainly reconstructed).
The Neptune Terrace, including its huge pool shell, are raised up behind massive retaining walls on the Hearst Castle ridge-line in the Santa Lucia Mountains. It is to the north and lower than the main Casa Grande and the guest house terrace, with vistas of the ranch, Point San Simeon coastline, and Pacific Ocean.
In 2014, the pool was drained due to severe drought conditions in Southern California. The pool had been leaking and evaporating 5,000 gallons of water per day. 
Designed by architect Julia Morgan, the Neptune Pool with terrace elements was started in 1924. The Neptune Pool was built and rebuilt three times, each version a larger size. After the 1926 and 1934 redesigns and re-buildings, it was finally deemed completed by William Randolph Hearst in 1936.
The Neptune Pool is 58 feet (18 m) wide except for the 95 feet (29 m) width at the primary axis fountain—alcove section, and the secondary axis pool length is 104 feet (32 m). The depth varies from 3.5 feet (1.1 m) at the west 'shallow' end, to 10 feet (3.0 m) at pools' main drains.
The fountains and pool are fed by spring water piped from the Santa Lucia Mountains, and the pool alone holds 345,000 gallons of water.
Architectural and landscape elements
The swimming pool is surrounded by Ancient Roman Revival and Greek Revival style pavilions and colonnades. The pool's main axis centerpiece and north terminus is elaborated from parts of the façade of an Ancient Roman temple that William Randolph Hearst had purchased in Europe and imported to San Simeon. It is symmetrically framed by the colonnaded pavilions as the secondary axis' west and east terminus elements.
17th-century Italian Neoclassical bas-reliefs are upon the sides of the colonnades. The 'Neptune' and 'Nereid' statues, first atop the cascade, were moved to present positions in the Roman temple's pediment. New classical sculptures were commissioned by sculptor Charles Cassou. His 'Neptune statuary group,' planned from the late 1920s for a small cascade pool, was never installed. His ‘Venus’ was.
In films and on television
- The Neptune pool was used as set for the entrance of Crassus' villa in Kubrick's Spartacus
- The Lady Gaga video "G.U.Y." was shot at various locations at Hearst Castle, including the pool. Due to drought conditions and leaks in the pool, the Neptune Pool was drained in 2014. However, the pool was filled for the music video.
- Lieu, Amy. "Drought Prompts Hearst Castle to Close Restrooms, Drain Pool". KCET.
- Hearstcastle.org: "Neptune Pool" . accessed 10.1.2012
- Hollywood Escapes: The Moviegoer's Guide to Exploring Southern California's Great Outdoors. p. 109.
- "Drought forces Hearst Castle to pool resources". San Louis Obispo Tribune. February 4, 2014.
- Ami Lieu (July 2, 2014). "Drought prompts Hearst Castle to close restrooms, drain pool". Social Wanderer. KCET.
- Linn, Sarah (February 11, 2014). "Hearst Castle goes Gaga as pop diva shoots video this week at estate". The Cambrian. Retrieved March 31, 2014.
- Shyam Dodge (April 15, 2014). "Lady Gaga denies claim she 'wasted 356K gallons of water to fill massive pool at Hearst Castle' during worst drought in California history". MailOnline.com (Daily Mail).
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