For lovers of early American literature, a trip to Concord isn't complete without a pilgrimage to Henry David Thoreau's most famous residence. Here, in 1845, at age 28, Thoreau moved into a one-room cabin—built for $28.12—on the shore of this 100-foot-deep kettle hole formed by the retreat of an ancient glacier. Living alone for the next two years, Thoreau discovered the benefits of solitude and the beauties of nature. The essays in Walden, published in 1854, are a mixture of philosophy, nature writing, and proto-ecology. The site of the first cabin is staked out in stone. A full-size, authentically furnished replica of the cabin stands about ½ mile from the original site, near the Walden Pond State Reservation parking lot. Even when it's closed, you can peek through its windows. Now, as in Thoreau's time, the pond is a delightful summertime spot for swimming, fishing, and rowing, and there's hiking in the nearby woods. To get to Walden Pond State Reservation from the center of Concord—a trip of only 1½ mile—take Concord's Main Street a block west from Monument Square, turn left onto Walden Street, and head for the intersection of Highways 2 and 126. Cross over Highway 2 onto Highway 126, heading south for ½ mile.