彩岩国家湖滨区的岩洞，密歇根 Cavern in Pictured Rocks National Lakeshore on Lake Superior, Michigan (© Kenneth Keifer/Getty Images)

彩岩国家湖滨区的岩洞，密歇根 Cavern in Pictured Rocks National Lakeshore on Lake Superior, Michigan (© Kenneth Keifer/Getty Images)

At the shore of an inland sea

We're looking out from a cavern at Pictured Rocks National Lakeshore in Michigan's Upper Peninsula. The area's named for its colorful sandstone cliffs, which stretch for 15 miles along the shores of the largest of the Great Lakes, Lake Superior. As groundwater leaches out of the rocks, it carries minerals such as iron, manganese, and copper that paint the cliffs in shades of red, pink, black, green, and other colors. The park itself, which is roughly the size of five Manhattans, boasts waterfalls, beaches, and rock formations—some resembling human profiles and castle turrets—carved over time by the relentless waves and unforgiving weather of Yooper Country.