12. Royalton Saint Lucia, Resort & Spa-Cap Estate, St. Lucia

Hotels.com average guest rating: 4/5

Price: From $383/night

The Royalton St. Lucia is not an entirely adult-only resort. However, it does have a separate 166-room section, known as "The Hideaway," which is kept entirely separate for adult guests. When it comes to eating or hitting the spa, they will have to mingle with others.