a) Agate Fossil Beds National Monument is a U.S. National Monument near Harrison, Nebraska. The main features of the monument are a valley of the Niobrara River and the fossils found on Carnegie Hill and University Hill. The area largely consists of grass-covered plains. Plants on the site include prairie sandreed, blue grama, little bluestem and needle and thread grass, and the wildflowers lupin, spiderwort, western wallflower and sunflowers.  The site is best known for the large number of well-preserved Miocene fossils, many of which were found at dig sites on Carnegie and University Hills. Fossils from the site, which date from about 20 million years ago, are among some of the best specimens of Miocene mammals.

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b) Wind Cave National Park: The Cave is in the southwestern corner of South Dakota north of Hot Springs. It's known for the vast, underground Wind Cave, with chambers like the Post Office and the Elks Room. Many of the cave’s walls are rich in honeycomb-shaped calcite formations known as boxwork. The park's prairie and pine forests are home to bison, elk and pronghorn antelopes. Trails include Rankin Ridge, with views of the Black Hills. Approximately 95 percent of the world's discovered boxwork formations are found in Wind Cave. Wind Cave is also known for its frostwork. The cave is also considered a three-dimensional maze cave, recognized as the densest (greatest passage volume per cubic mile) cave system in the world. The cave is currently the sixth-longest in the world with 140.47 miles (226.06 km) of explored cave passageways. Above ground, the park includes the largest remaining natural mixed-grass prairie in the United States