Interlaken, one of the Alps' original resorts, is a useful springboard for alpine thrills. And, when the famous peaks get socked in by clouds, you can choose from some interesting lowland options. In this town, four innocent-looking hay barns conceal a network of tunnels connecting several big guns. Many of these once top-secret sites are now open to the public as museums. For more information on the Rick Steves' Europe TV series — including episode descriptions, scripts, participating stations, travel information on destinations and more — visit www.ricksteves.com.