When you drive through the Madras region on U.S. Highway 97, you see a gently rolling plain dotted with low hills and flat-topped buttes. Since the plain appears to extend westward uninterruptedly to the foothills of the Cascade Range, little would you imagine that between you and the mountains lurk three awesome canyons, totally invisible until you nearly reach the brink. Three rivers -- the Deschutes, the Crooked, and the Metolius - have cut these gashes into the plain and have laid open for observation a sequence of remarkable geologic events. The place where the three rivers join to make one canyon marks the general location of the Cove Palisades State Park. Cove Palisades State Park encompasses Round Butte Dam and its reservoir, Lake Billy Chinook. The 7,000-acre park features picnicking, camping, and boating facilities on the shore of the lake and scenic viewpoints on the canyon rims. The park is an excellent place to see 10 million years of geologic history. The purpose of this report is to present the geologic background of the park area in a nontechnical way (assisted by a short glossary of terms), and then to outline a geologic motor tour of the park by means of descriptive text, photographs, cross sections, and maps. The self-conducted tour starts at Madras, makes 12 designated stops, and ends on the far side of the park in the canyon of the Deschutes River, a total distance of about 25 miles.