Mount Merapi — "Mountain of Fire" — rises to 2,930 metres on the northern edge of Sleman and is among the most active volcanoes on earth. It erupts every few years, with a major catastrophic event roughly every decade. The 2010 eruption killed more than 350 people and changed the shape of the summit cone.
For visitors, Merapi is approached from the Kaliurang resort area. Jeep tours run along the lava-scarred lower slopes, and the Merapi Volcano Museum at the foot covers the geology and the human cost of its eruptions. Climbing to the rim is sometimes possible from the northern Selo side when activity is low, but check the current alert level before planning anything.