The blasted lunar landscape of PARQUE NACIONAL VOLCÁN IRAZÚ (daily 8am–3.30pm; $10; t 2200-5025) reaches its highest point at 3432m and, on clear days, offers fantastic views all the way to the Caribbean coast. Famous for having had the gall to erupt on the day President John F. Kennedy visited Costa Rica on March 19, 1963, Irazú has been more or less calm ever since. But while its main crater is far less active, in terms of bubblings and rumblings, than that of Volcán Poás, its deep depression and the strange algae-green lake that fills it create an undeniably dramatic sight.
Looming 32km north of Cartago, the volcano makes for a long and entirely uphill but scenic trip, especially in the early morning before the inevitable clouds roll in (about 10am). While the main crater draws the crowds, it’s worth noting that the shallow bowl to its right, the flat-bottomed and largely unimpressive Diego de la Haya crater, is the remnant of Irazú’s first and largest eruption: when it blew in 1723, the eruption lasted ten months and showered San José in ash.
There’s not much to do around here after viewing the main crater from the mirador – no official trails cut through this section of the park, though you can scramble among the grey ash dunes that have built up on Playa Hermosa, the buried older crater that spreads to the left of the walkway and is dotted with what little vegetation that can survive in this otherworldly environment. Stay behind the barriers at all times, though, as volcanic ash crumbles easily, and you could end up falling into the ominous-looking lake.