Arenal is a near-perfect volcanic cone in northern Costa Rica, and for forty-two years it put on a show: from 1968 until 2010 it glowed with lava almost every night. Then it stopped. The eruption that started all of it did not go up. In 1968 the mountain burst sideways out of its western flank with almost no warning, opening three craters at once, twelve years before Mount St Helens failed the same way. Three villages on that side were buried, and the town on the eastern side was not touched. It is called La Fortuna, the fortune, and everyone tells you the name came from surviving that night. It was actually given years earlier, for the fertile land. The cone still fills the sky above the town, and the hour to see it is just after dawn, before the day's cloud climbs up from the lowlands and covers the summit.
The heat that fed all of that is still in the ground. Rivers on the flanks run hot enough to sink into, and you ease into water that comes off the mountain already warm, the forest steaming around you and the jungle loud on every side after dark. Suspended walkways cross the steep rainforest ravines, lifting you level with the treetops where most of the forest's life actually goes on. Sloths and nesting birds hold still in the branches, and on the longest spans the cone stands framed at the far end. A long stepped path drops through dripping forest to La Fortuna Waterfall, a single ribbon falling about seventy metres off a dark cliff into a churning pool. The spray keeps the whole gorge cool and loud, and you can swim in the calmer water to one side before facing the climb back up. Park trails also run out onto the lava the volcano threw down during its active decades. The rock is still black and sharp underfoot. It is already splitting open to ferns, young trees and basking lizards, and from the edge of the flow the forest and the cone rise together.