The thrilling rush of river in this deep-sided gorge (I-93, exit 34A, Franconia Notch State Park, 603/745-8391, www.flumegorge.com, 9 a.m.–5 p.m. daily May–Oct.; until 5:30 p.m. July–Aug., $13 adults, $9 children 6–12, free children 5 and under) has been a tourist attraction since it was discovered in the 19th century. A wooden walkway suspended along the side of the cliff takes visitors alongside the rushing stream, past whirlpools and waterfalls and over two covered bridges before ending in a pleasant forest trail loop.

If you’ve ever ridden a flume ride at an amusement park, you’ll get the basic idea. A “flume” is a geological feature formed when a plug of basalt is worn away from between two walls of harder granite—the result is a torrent of water in a steep gorge.

While this flume gorge isn’t the only one in the region, it is notable for its size and ferocity, stretching almost three football fields in length, with 70- to 90-foot-high rock cliffs on either side.