Open since 1980, Harrah's -- located in Atlantic City's Marina District -- completed a $500 million expansion in 2008, which included the addition of a new 44-story Waterfront Tower with contemporary furnishings and bay views. The resort offers 2,590 rooms in five towers (older rooms are in major need of renovations) as well as a slew of impressive amenities. Unlike at other Atlantic City resorts, the casino is not the main draw here; rather, action is centered in the adults-only indoor pool, a glass-domed oasis with constant 82-degree temperatures and tropical plants. At night it becomes "The Pool after Dark," a lively club scene with DJs and occasional celeb appearances. Other highlights include a Viking Cooking School, Elizabeth Arden Red Door Spa, and gourmet restaurants. But it's not within walking distance of the beach or boardwalk, and there are fees for Wi-Fi and parking.