A few years ago, my husband and I visited this very well known hiking trail in Franconia Notch, NH on our way home from a memorial service in Vermont. It has hiking trails down the mountain alongside the Pemigewasset River, ending in a large pothole that is 30 feet in diameter and 15 feet deep, seen here. It had its beginning some 25,000 years ago as the Ice Age came to a close. Water flowing from the melting glacier that filled Franconia Notch eroded the solid granite bedrock. During the thousands of years that followed sand and stones were whirled around by the force of the river causing a boring action that left the sidewalls smooth. The rock formation seen in the stream bed at the outlet has been known for generations as "The Old Man's Foot". The great American naturalist, Henry David Thoreau (1817-62), on his first trip to the White Mountains in September of 1839 stood here, as you do, and watched the water cascade into the granite bowl and whirlpool around its walls. He would later write in his Journal, "this pothole is perhaps the most remarkable curiosity of its kind in New England." Samuel Eastman in his 1858 White Mountain Guide called this spot "One of the beautiful haunts of Nature, a luxurious and delicious bath fit for the ablutions of a goddess." The Basin can be accessed from the northbound and southbound directions. There are picnic tables and walking paths, as well as hiking trails. It is said the Native Americans once bathed in this in this natural pool. Taken with my Canon EOS 90D. f/3.5, 1/15 sec., ISO-100, 0 step, 18mm, 3.625 max ap, no flash, no tripod.