Volcano Craters

Almost all of these are in Iceland — the northeast around Mývatn, the south, the west around Snæfellsnes and Borgarfjörður, and the Reykjanes Peninsula — with one outlier in Valencia, the Cofrentes volcano. The shapes vary more than the name suggests: tuff rings a kilometre across, spatter cones, red rootless cones on the edge of Reykjavík, lava fields of hollow pillars left by drained magma. Several have stepped paths or a metal staircase to the rim; the highland ones, Askja and Mælifell among them, sit on F-roads open only in summer and passable only by 4x4.