Looming on the horizon 19km northeast of Cartago, 3432m Irazú – which derives its name from the indigenous word ara-tzu (thunder point) – is the largest and highest active volcano in Costa Rica and one of the few you can currently hike around. In 1723 the Spanish governor of the area, Diego de la Haya Fernández, watched helplessly as the volcano unleashed its destruction on the city of Cartago (one of the craters is named in his honor). Since the 18th century, 15 major eruptions have been recorded. At the time of research the volcano was slumbering peacefully.
The summit is a bare landscape of volcanic-ash craters. The principal crater is 1050m across and 300m deep; the adjacent Diego de la Haya Crater is 690m across and 80m deep; and the shallowest, Playa Hermosa Crater, is being colonized by sparse vegetation. There's also a pyroclastic cone, consisting of rocks fragmented by volcanic activity.