Rising straight out of the northern lowlands of Costa Rica, Arenal Volcano is an almost perfectly symmetrical cone, its dark slopes ringed by dense rainforest and naturally heated rivers. In the cool hour just after dawn, before moisture rises from the plains to wrap the peak in cloud, the bare triangular summit stands sharp against the morning sky above the town of La Fortuna. Below it, the terrain gives way to thick rainforest, where trails and high suspension bridges bring you level with the canopy. Sloths hang motionless in the cecropia branches, keel-billed toucans glide between the trees, and the deep roars of howler monkeys echo across the ravines. Trails continue onto the jagged black lava fields thrown down across the volcano's western flank during its twentieth-century eruptions. Walking across these brittle ridges of dark basalt, you find bright green ferns already splitting through the stone, showing how quickly the jungle reclaims the ground the mountain once buried.
Arenal has been quiet since 2010, but the magma chamber deep below has never cooled, and subterranean heat still governs daily life around the mountain. Rain sinking into the porous slopes filters through superheated rock and returns to the surface as mineral-rich thermal water. In jungle rivers like the Tabacón, warm currents flow through stepped rock pools shaded by overhanging palms, creating natural thermal baths heated directly by the volcano. Further down the foothills, a steep staircase descends through dripping forest to La Fortuna Waterfall, where a seventy-metre cascade plunges into a cold, jade pool. Climbing the crater itself is strictly forbidden for safety, and park trails remain on the lower slopes. Yet walking beneath Arenal's towering silhouette offers something far more compelling than reaching a summit: the quiet presence of a sleeping giant that continues to warm, feed, and sustain the wild green world at its feet.