Indonesia's Kawah Ijen Volcano, which glows with an otherworldly "blue lava" at night. The mountain contains large amounts of pure sulfur, which emits an icy violet color as it burns, turning the rocky slopes into a hot (at least 239 degrees Fahrenheit), highly toxic environment.
Víti Lake Víti (the little one on this picture) aside Öskjuvatn (the big one) at the Askja Vulcano. If I remember right you can swimm in Víti. If you look closely you can see some tourists around the crater. Víti means hell on icelandic for lake Víti is known as one of the gates to hell. (: Askja, Iceland
Hawaii Volcanoes National Park is one of two national parks in America's 50th state, and one of a number of national parks dedicated to volcanism and its effects. Located about 90 miles from Hilo on the southern section of the big island of Hawaii, the park contains 229,177 acres and features two active volcanoes, volcanic craters and caldera, rain forests, wildlife including rare birds, and lush vegetation, some of which is endemic to the islands.