The Lava River Cave near Bend, Oregon, is part of the Newberry National Volcanic Monument, which is managed by the United States Forest Service.

At 5,211 feet (1,588 m) in length, the northwest section of the cave is the longest continuous lava tube in Oregon.

Small rivulets of water carry the sand downhill, plugging the far end of the cave with sediment.

[2] The Lava River Cave is located 12 miles (19 km) south of Bend on the east side of Highway 97.

[3][4] The forest surrounding the cave entrance is dominated by large ponderosa pine trees with sagebrush, manzanita, bitterbrush, snowbrush, and chokecherries as the main ground cover.

Along the short path leading from the forest floor down to the cave entrance, visitors will also find serviceberry, false Solomon seal, squaw currant, Oregon grape, and small willow trees.

In 1991, park personnel observed a full-grown cougar run out of the cave entrance area, but that was a single sighting.

Small resident birds include wrens, robins, juncos, thrushes, woodpeckers, sapsuckers, red-shafted flickers, and ruby-crowned kinglets.

Larger birds include great horned owls, red-tailed hawks, vultures, and a few golden eagles.

[2] Forest Service biologists have identified several species of harvestmen, worms, centipedes, and millipedes that live inside the cave.

In fact, bats usually remain in hibernation until July, and when active they are nocturnal so they are asleep during the day when the cave is open.

Waking it from hibernation is extremely stressful, and can cause the bat to die from the sudden expenditure of energy.

The first recorded discovery is credited to a local settler named Leander Dillman, who found the cave opening on a hunting trip in 1889.

[6] In 1926, the Shevlin-Hixon Lumber Company donated the 22.5-acre (91,000 m2) site around the cave entrance to the State of Oregon for a park.

In 1981, the cave and above ground park area were acquired by the Forest Service as part of a land exchange with the State government.

The main section runs gradually downhill 5,211 feet (1,588 m) in a northwesterly direction from the entrance, passing under Highway 97.

At the end of Low Bridge area, the tube begins to narrow and the cave is divided into two tunnels with intermittent connecting passages.

Rain and melting snow carried the ash down from the surface through cracks in the rock and deposited it on the floor of the cave one grain at a time.

Since it takes hundreds of years to build these delicate sand forms, the Forest Service has fenced off the garden area to protect it.

As a result, the Forest Service strongly recommends that visitors wear a warm jacket while exploring the cave.

Personal lanterns are also permitted; however, in order to protect the cave's fragile environment, they cannot have glass globes or use kerosene or white gas.