At the foot of Arenal Volcano, Tabacon Thermal Resort & Spa is immersed in rainforest threaded by naturally heated mineral springs. Rooms and suites use timber, local stone and broad windows to frame dense tropical planting, while the property’s thermal river forms a sequence of pools, cascades and secluded bathing pockets beneath the canopy. Shangri-La Gardens provides an adults-only section of the springs, and the open-air spa places treatment bungalows among the trees. Restaurants draw on Costa Rican produce, with terraces and paths leading back towards the river’s warm current and volcanic rock.