Michael Schroeder, Special To The Washington Post Weeks before I actually headed to Mammoth Cave National Park for a weekend trip, and a day after I’d booked several guided cave tours, I encircled my chest with a tape measure. I was relieved to confirm I’d be an OK fit — quite literally, if just barely — for the Wild Cave Tour, the longest, most intensive cave tour offered at the Kentucky park. The guided tour at the UNESCO World Heritage site involved more than five hours of hiking in massive caverns, shinnying up and down twisted passageways, clambering over boulders, and belly-crawling through exceedingly tight sections of rock that wouldn’t give an inch.