This 236,381 acre park in Washington state happens to encompass an active volcano, but since it last erupted in the 19th-century, chances are nothing will happen if you go—nothing, that is, except experiencing breathtaking views of Mt Rainier itself, along with glaciers, waterfalls and meadows filled with wildflowers.
Best time to visit: July through August, when wildflowers transform the park's subalpine meadows and the dry, warm weather provides optimal hiking conditions.