Mushroom Rock State Park: Marquette, Kansas

Off the Prairie Trail Scenic Byway, way down a ribbon of dirt road, is the smallest state park in Kansas: five acres surrounding a few ancient rocks weathered into mushroom form. They are the remains of a 100-million-year-old beach. Long ago, a vanished sea whooshed in limy minerals, which mixed with sand, creating pockets of natural concrete. Over time, the surrounding softer sandstone was worn away by wind and water, and the mushroom forms remained.

V. cool to visit and gently touch the rocks (which are covered with marks from centuries of passersby; they were a well-known and well-used landmark).