10. Hearst Castle Neptune Pool – California, USA
Built in the 1920s for newspaper tycoon William Randolph Hearst, this Greco-Roman masterpiece holds 345,000 gallons of spring-fed water. Surrounded by limestone colonnades, Roman statues, and marble staircases, it’s part museum, part swimming pool. Celebrities and dignitaries once lounged here under California skies. Today, it remains a stunning tribute to old Hollywood grandeur.