Deep inside the Siskiyou mountains lies the "Marble Halls of Oregon." The caves formed when acidic rainwater dissolved the surrounding marble, creating one of the few marble caves in the world.

There are 17 national wildlife refuges and preserves dotted across the state. One of the country's biggest game preserves is Sully's Hill, where bison, elk, and deer can be seen in their natural environment.

Oregon offers the vacationer a panorama of sandy beaches broken by rocky cliffs, lofty snow-clad peaks towering over broad river valleys, narrow canyons, rushing streams, peaceful lakes, and dense forests. It also provides ideal opportunities for outdoor activities.

Dominated by Mount Hood, the most popular recreation area, the spectacular mountain terrain challenges skiers in winter and hikers and climbers in summer. An abundance of wildlife in the vast forests include deer, elk, small animals, and birds. Trout, salmon, bass, perch, and other game fish are plentiful in Oregon's lakes and streams. Along the coast are sheltered coves for swimming and clam digging, vast stretches of sand dunes, and forbidding cliffs with huge caves formed by the crashing breakers.

Oregon's only national park, Crater Lake National Park, surrounds an extinct volcano, Mount Mazama, on the crest of the Cascade Range. The deep crater, rimmed with high jagged cliffs, encloses one of the world's most beautiful and deepest lakes. Crater Lake, which is about 6 miiles across and 1932 ft deep, is renowned for its unique setting and its brilliant blue color. On Mount Elijah in the Siskiyou Mountains is Oregon Caves National Monument, where pillars and stalactites of calcite line passageways and hang from vaulted domes. The world-renowned John Day Fossil Beds National Monument in central Oregon is home to a well-preserved fossil record of plants and animals that spans more than 40 million of the 65 million years of the Cenozoic Era, or Age of Mammals.

The federal government also acts to preserve the Columbia River Gorge, a spectacular river canyon that cuts through the Cascade Mountains and is especially popular with windsurfers.

The Oregon Dunes National Recreation Area is on the coast between the Siuslaw River and Coos Bay in the Siuslaw National Forest, one of only two national forests that border the Pacific Ocean.

Oregon's 13 national forests cover more than 15 million acres and offer camping and many recreational facilities. There are 36 wilderness areas. The largest national forest is Wallowa-Whitman National Forest in the northeastern part of the state. The largest unbroken area of national forests runs in a continuous chain throughout most of the Cascade Range. The Wallowa-Whitman shares with Idaho one of the deepest gorges in the world, Hells Canyon. Crooked River National Grassland is in north central Oregon.

The Siuslaw National Forest extends from Tillamook to Coos County in three separate units and contains some of the most productive tree-growing land in the United States. The Deschutes National Forest, located on the eastern flank of the Cascade Mountains in central Oregon, is one of the most popular forests in the Pacific Northwest because of its wide variety of recreational opportunities, besides providing commodities ranging from timber to mushrooms. The Rogue River National Forest consists of two separate units of land. The western unit of the forest includes the headwaters of the Applegate River in the Siskiyou Mountains. To the east, the forest includes the upper reaches of the Rogue River, in the Cascade Mountains.

Other national forests in Oregon include the Fremont, Malheur, Mount Hood, Ochoco, Siskiyou, Umatilla, Umpqua, Willamette, and Winema.