You might be surprised to find one of the largest reservoir lakes in the state here. The lake was formed as a result of the Amstad Dam, an international cooperative project completed in 1969. With an astounding 547 miles of shoreline (on the Texas side), the lake offers a respite from the desert heat for swimmers, freshwater scuba divers, and boaters; the latter can explore the lake's coves and walled canyons, or take to the open waters and rivers in canoes, kayaks, or motorized watercrafts. Because of its location, the park has a remarkable vantage point for observing birds both native and migratory, from waterfowl to the zone-tailed hawk. Another unique attraction among the state’s lakes are prehistoric Native American paintings and pictographs dating back at least 4,000 years; reach them by boat, on foot, or on a guided tour.