6. Colorado

Rocky Mountain National Park

Colorado

In the U.S.’s highest park, altitudes range from 7,500 to 14,000 feet.

There are 350 trails throughout the park, some leading you up to tundra areas where few plants grow but animals roam freely.

More experienced hikers can head to Flattop Mountain or Estes Cone, both over 11,000 feet.

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