Most folks think Iowa is just endless corn. Oak Grove proves them wrong. Right along the Big Sioux River, the terrain suddenly drops off into steep, tree-choked ravines. Wind-blown silt called loess formed these huge bluffs thousands of years ago, giving the park some serious elevation changes. Tough hiking. You'll sweat climbing up from the muddy bank, but standing up top and looking clear across the water into South Dakota makes it worth the lung-burn.

Paddlers come here constantly. Throw a kayak into the river and let the brown current pull you along for three hours. Catfish hide in the deep pools near old, submerged logjams. Bring stinkbait. Iowa made this area a state park way back in 1924, so it carries a neat bit of local history. Though honestly, most people just come to pitch a tent under the bur oaks. Dark skies. Great fire pits. Just pack strong bug spray, because the July mosquitoes do not mess around.