Tabacón Thermal Resort and Spa

"On the west side of Arenal Volcano, this 900-acre tropical reserve was a labor of love for owner and architect Jaime Mikowski, who spent years planting acres of native plants and coaxing the land’s natural mineral springs into a river that now flows throughout the property, spilling over into dozens of waterfalls and pools that range from 72 to 105 degrees. Spacious rooms have marble floors and streamlined furnishings; splurge on a suite, which features a private terrace and a Jacuzzi tub—a little superfluous considering all the other options for soaking in warm water here, but who’s complaining? There are also five swimming pools, one with a swim-up bar and waterslide, and a spa comprising 12 bungalows with treatments that all include, you guessed it, a dip in a thermal spring-fed tub. While the property is also open to day trippers, guests of the resort have exclusive access to Shangri-La Gardens, an adults-only lounge area with pools, cabanas, and a folliage-filled bar."