Oregon Caves National Monument
Nestled deep inside the Siskiyou Mountains, the caves formed as rainwater from the ancient forest above dissolved the surrounding marble and created one of the world's few marble caves. The highly complex geology found on the Monument contributes to the unusual and rare plants and animals found nowhere else but here. Experience the extensively decorated and adventurous "Marble Halls of Oregon."
As seen on http://www.nps.gov/orca/index.htm

Marble Mountain Ranch
Somes Bar, California
Dude ranch vacations at Marble Mountain Ranch have a "Saddle and Paddle" or "Raft&Ride" theme. We combine horseback mountain trail riding vacations with thrilling whitewater rafting, kayaking, shooting sports, fly fishing, jet boat adventures on the Klamath River and legend Western hospitality.