It doesn't have class IV rapids but that doesn't matter. The Boise River's lazy serpentine through the heart of downtown Boise makes it half-tour guide, half-amusement park ride--entertainment au natural for locals and out-of-town guests all summer long. Be on the lookout for wildlife like blue herons, river otters, and hotties from Boise Fire Department's dive team who train on the river several times each week.
Second Place: Greenbelt
Third Place: Table Rock