This nature reserve surrounds the Badlands and together they protect the country's largest prairie grasslands, several species of Great Plains mammal (including bison and black-footed ferret), prairie falcons and lots of snakes. The National Grasslands Visitors Center has good displays on the wealth of life in this complex ecosystem. Rangers can map out back-road routes that will let you do looping tours of Badlands National Park and the grasslands without ever touching I-90.