A National Natural Landmark, Mammoth Spring is one of the world’s largest springs with nine million gallons of water flowing hourly. It forms a 10-acre lake then runs southward as the Spring River, a famous Ozark trout and float stream. Remnants of a mill and hydroelectric plant are part of Mammoth Spring’s history. The park also features an 1886 Frisco train depot and museum. Adding to the things to do here are a playground, picnic area, baseball field, walking trail, Arkansas Welcome Center, and gift shop.