There are local hiking trails that are fun to walk on.  Then there are the best hiking trails in the world including the Grand Canyon Rim to Rim in Arizona.  24 challenging miles with heat, dehydration risk and rattlesnakes, but worth the risk.

The Narrows in Zion National Park in Utah is another fun hiking trail.  Narrows' sandstone slot canyons and a river make for an amazing 16 miles.  How about the Overland Track in Australia.  About 8,000 hikers a year pass mountains, rain forests and plains on this six-day hike.

Let me tell you about one more.  Tour du Mont Blanc, Switzerland/Italy/France.  Europe's popular Alpine hike passes through three countries and typically takes 10 days.