Regardless of location—a city center, a dunes-blanketed desert, or a private tropical isle—the heart of a hotel is often its swimming pool. It serves as a social ground zero, where guests can see and be seen, mingle, and relax and recharge: essential pursuits, especially in these postholiday wintry months. A well-designed pool is almost as important as the hotel itself, which is why AD has scoured the globe for the most awe-inspiring watering holes. From an Art Deco Miami masterpiece to a Mediterranean icon to a technological wonder overlooking the Hong Kong skyline, these 15 hotel pools are sure to dazzle and inspire. Dive in!