Yet the tunnels weren't only a strategic weapon: Inside the nearly 125-mile tunnel network, dug by hand and ingeniously booby-trapped for protection, people lived and worked. Once the tunnels were discovered during the war, teams of American and Australian soldiers known as Tunnel Rats infiltrated them, sometimes crawling through spaces as little as 12 inches wide to recover military information and supplies.

Today the Cu Chi Tunnels are a day trip from Ho Chi Minh City (formerly Saigon) and are part of most tour programs to the area, such as the Vietnam Cultural Explorer tour offered by Boundless Journeys. Yes, the tunnels still arouse strong feelings and opinions about politics and war, but beyond that they are a tremendous testament to people's resilience and resourcefulness during wartime. They also will put your fear of enclosed spaces into perspective.

Afraid of the dead? Cambridge, Massachusetts

Don't think of Mount Auburn as a cemetery. Think of it as a well-tended horticultural park with pretty one- and two-mile walking trails and lots of beautiful New England foliage from blazing red Black Gum trees to fall-blooming Witch Hazel to 26 different species of oak. That's sort of what its founders had in mind when, in 1831, the Massachusetts Horticultural Society purchased the 72 acres that would become Mount Auburn Cemetery.

You can choose to see Mount Auburn purely as a park. The visitor's center sells maps for self-guided theme tours on horticulture, architecture, art, and other topics, and runs excellent docent-led tours on weekends. Eventually, though, you're bound to become curious about the people at rest in Mount Auburn, and you'll find that they include outstanding figures from all fields of endeavor, including poet Henry Wadsworth Longfellow; Fannie Farmer, creator of the "Boston Cooking-School Cookbook"; scientists and thought pioneers such as Buckminster Fuller, B.F. Skinner, and Mary Baker Eddy; as well as jurists, artists, statesmen and business leaders.

You'll also learn (thanks to the "Not So Rich and Famous" guided tour) that many of the ordinary folks buried here have fascinating life stories as well. "We return to the world, and we feel ourselves purer, and better, and wiser, from this communion with the dead," said Joseph Story in 1831 when the cemetery was consecrated. Those remain words to live by.