Lassen Volcanic National Park in Northern California is one of the few places on Earth where all four types of volcanoes can be found in a single region. Steaming fumaroles, boiling mudpots, and clear mountain lakes dot its wild landscape. The park centers on Lassen Peak, the world's largest plug-dome volcano, which last erupted from 1914 to 1917. Visitors can explore forests, wildflower meadows, and hydrothermal areas in relative solitude.