You round a switchback and the air suddenly feels thinner — cooler and clean enough to bite. The van stops near the park gate and a low, basaltic landscape opens like a raw wound in the earth: the crater of Irazú, Costa Rica’s highest active volcano, sitting at 3,432 meters (11,260 ft). The guide pulls a windbreaker from the back of the vehicle and points up. The crater rim is a five- to 20‑minute walk from the parking area depending on how much you stop to take pictures, and the path goes over a moonlike surface of volcanic sand and jagged rock that seems to dare you to approach its edge.