The Underworld of Oregon Caves National Monument

Oregon Caves National Monument and Preserve is a protected area in the northern Siskiyou Mountains of southwestern Oregon in the United States. The 4,554-acre (1,843 ha) park, including the marble cave, is 20 miles (32 km) east of Cave Junction, on Oregon Route 46. The protected area, managed by the National Park Service (NPS), is in southwestern Josephine County, near the Oregon–California border.

Oregon Caves is a solutional cave, with passages totaling about 15,000 feet (4,600 m), formed in marble. The parent rock was originally limestone that metamorphosed to marble during the geologic processes that created the Klamath Mountains, including the Siskiyous. Although the limestone formed about 190 million years ago, the cave itself is no older than a few million years. Valued as a tourist cave, the cavern also has scientific value; sections of the cave that are not on tour routes contain fossils of national importance.

Activities at the park include cave touring, hiking, photography, and wildlife viewing. One of the park trails leads through the forest to Big Tree, which at 13 feet (4.0 m) is the widest Douglas fir known in Oregon. Lodging and food are available at The Chateau and in Cave Junction. Camping is available in the preserve at the Cave Creek Campground, at a local USFS campground, and private sites in the area.

Since the cave is only 44 °F (7 °C) inside regardless of the outdoor temperature, the NPS recommends warm clothing for its tours. Good walking shoes are needed to negotiate slippery and uneven surfaces. Not allowed on the tours are flashlights, backpacks, large purses, tripods, or pets. To protect bats from white nose syndrome, visitors must not take any clothing or equipment into Oregon Caves that have previously entered any other cave or mine.