This massive (and active) volcano is an Ometepe landmark. The seven- to 10-hour hike up loose volcanic stone to the summit of this looming peak can be tough, so be in good physical condition and bring water, snacks and real hiking shoes. Most hikes leave from either Moyogalpa or Altagracia. Remember that there's no shade above the tree line, it's even steeper than it looks, and it can get windy and cold at the top, particularly if it's cloudy out.
There are three main trails to the top: La Concha and La Flor (the most popular trail), both close to Moyogalpa, and La Sabana, a short distance from Altagracia. It's almost always cloudy at the top, which means your chances of seeing the fuming craters and awesome views over the lake and across Central America's volcanic spine are slim, even during dry season.
Guided treks up the volcano cost around US$25 to US$40 per person and can be organised by most outfitters on the island.