If your to-do wish list before shuffling off this mortal coil includes spelunking, you could do worse than explore the Marble Halls of Oregon.

If your to-do wish list before shuffling off this mortal coil includes spelunking, you could do worse than explore the Marble Halls of Oregon.

Officially known as the Oregon Caves National Monument, the caverns offer a path into the wondrous underground world of limestone formations and fossils from the distant past.

"For some folks, the caves can require a lot of bending and stooping — people will use muscles they weren't aware of," says George Herring, chief of interpretation.

Yet cave visitors have included hearty folks into their 90s, he said.

All told, the tour is just shy of a mile, with .6 of a mile in the caves and the remainder passing through an old-growth forest.

The only physical restriction is that cave visitors must be at least 42 inches tall so they can navigate the steps, he says.

"For anyone with a mobility concern, the first room can be reached with a (wheel) chair," he says.

The monument is in the Siskiyou Mountains at about 4,000 feet elevation some 20 miles east of Cave Junction in the Illinois Valley.

About 45,000 people each year take a tour of the caves.

The caves were declared a national monument by President William Howard Taft on July 12, 1909. The nearly 500-acre site is the state's first national monument.

Although likely long known by American Indians, the caves were discovered by Williams resident Elijah Davidson while bear hunting in fall 1874. The U.S. Forest Service managed the monument until 1933, when its administration was turned over to the National Park Service.

The 10-sided, six-story Oregon Caves chateau was built in 1934 by the Civilian Conservation Corps during the depths of the Great Depression. It's constructed of huge post-and-beam log framing on marble bedrock. Inside is a massive stone fireplace, along with oak-slab stairs and gnarled handrails fashioned from local hardwoods.

Flowing out of the caves is the tiny River Styx — you can jump across it — which forms a pool near the chateau before gurgling down the mountain.

The caves are open for tours from March through Nov. 4 this year. The charge for a cave tour is $8.50 for those 17 and older and $6 for those who are younger. Group rates are also offered.

The annual no-fee day will be May 12, although visitors are asked to bring some non-perishable food that the park service staff will donate to local charities.

There is no fee to enter the monument outside the caves any time of the year. Visitors can hike the trails and picnic at the monument's grounds or dine at the chateau.

But most visitors want to take a cave tour, which offers both beauty and a fascinating science lesson, Herring says.

"When you step inside the caves, you see geology from the inside out," he says.

The marble housing the caves formed about 250 million years ago, eventually creating a habitat for animals that are now long gone from the region, he says, citing fossilized remains found in the caves.

Consider the fossil bones of a grizzly bear found in the mid-1990s, he says.

"It is at least the second oldest ever found in North America," he says. "We know the bones are more than 50,000 years."

And there were the fossilized bones of a jaguar, a cat that roamed the area an estimated 38,500 years ago, he notes.

"It is the northernmost jaguar found — it would have been an Ice Age cat," he says.

"You have to scrub your imagination what the ecosystem was like when you start considering the fossils we've found here."

For more information on the caves or the chateau, see www.nps.gov/orca or www.oregoncaveschateau.com.

Reach reporter Paul Fattig at 541-776-4496 or email him at pfattig@mailtribune.com.