The Christmas Valley Sand Dunes Area of Critical Environmental Concern (ACEC) in south-central Oregon is the largest inland shifting sand dune system in the Pacific Northwest . It is a popular destination for off-highway vehicle enthusiasts with nearly 8,900 acres of the Sand Dunes site open to vehicle use. Nearby, the Lost Forest Research Natural Area is an unusual stand of ancient ponderosa pine forest, the remnant of a forest that existed in a cooler and wetter age. Another facet of the ACEC is Fossil Lake, the site of paleontological work for more than 100 years and where hundreds of species of reptiles, birds, fish, and mammals have been identified. Know Before You Go: Off-Highway Vehicles (OHVs) are allowed only on designated routes or areas. Oregon ATV permits required Camping is Allowed in designated sites only. Sites are primitive with no facilities, water, or restrooms provided. Firewood Collecting or Cutting is PROHIBITED. The Fossil Lake Area is CLOSED to OHVs. Collecting Fossils by the public is STRICTLY PROHIBITED throughout the Fossil Lake Area. The Nearest Services are located in Christmas Valley, Oregon, approximately 16 miles southwest. Point of Interest: Fossils found at nearby Fossil Lake range in age from about 10,000 years to as much as 400,000 years. Access to this special area is limited to walk-in traffic only.