Bruneau Dunes in Mountain Home, Idaho

Bruneau Dunes lie in the Eagle Cove Depression, an ancient cut-off meander of the Snake River. The initial sand deposits were left by the Bonneville Flood around 15,000 years ago, when Pleistocene Lake Bonneville in Utah overtopped a low pass and sent a huge flood down the Snake drainage. Since then, statistically balanced northwest and southeast winds have kept the sand from dispersing, instead sweeping it together to form substantial dunes. In fact, the 470-foot (143 meter) Big Dune is the tallest single-structured sand dune in North America.

A network of trails extends through the park, including the dunes, and hikers are welcome to climb the dunes. Dogs on lead are also OK and are permitted on the dunes, but please clean up after your pet. A popular activity is riding a sandboard (basically an old snowboard) down a dune, and sandboards can even be rented at the Visitor Center. Many trails are also open to horses, and an equestrian campground with horse trailer parking sits on the west side of the park, south of the Visitor Center. No motorized activity is permitted on the dunes. 

Two attractive lakes, Big Lake and Small Lake, lie at the foot of the main dunes on the north. These lakes are a twentieth-century phenomenon; they resulted from a substantial rise in the water table due to the extensive irrigation developments along the Snake River. They are open to non-motorized craft and also to fishing.

Perhaps most unusually, Bruneau Dunes State Park hosts an observatory that is accessible to the public. Because of effectively being situated in a hollow, down near the Snake River, the area is a dark-sky site, with the city light of Mountain Home (about 20 miles north) screened by the rim above the river. Astronomical presentations are typically given on Friday and Saturday nights from late spring into early fall, and visitors will get a chance to look through a variety of telescopes, including the new CDK 700 27-inch reflector. This is said to be the largest publicly accessible telescope in Idaho.