This 600-acre ecolodge is named for the “lost river” flowing through a canyon 150 feet below and dotted with dozens of soothing warm mineral pools thanks to the geothermal activity of nearby Miravalles Volcano. The first thing guests see as they approach the lodge is a large wood-and-steel rotunda that from a distance resembles a flying saucer hovering just above the surrounding dry forest, a multiaward-winning design that houses the open-air restaurant/bar and spa. The bungalows too are just above ground; the 20 prefabricated cubes are suspended on seven pylons, so no trees were cleared in the building process. Rooms are basic, but with a clean, airy, modern design. Each features two rolling beds that can be pushed together to make one larger bed; a rollaway can accommodate a third guest or child (though no one under the age of eight is allowed). Soak in the property’s natural thermal springs, or try the three naturally heated pools with swim-up bars. Work up an appetite hiking, tubing on the river, or challenging the mountain-bike course or the cable-based “canyon adventure.” The restaurant features satisfying fare that highlights seafood and Costa Rican specialties, which guests can arrange to enjoy from a platform that sits 160 feet above the river.