I had visited The Lost River in North Woodstock several times in my early years (see here) so we decided to take Alex there since we have all been vaccinated. Make sure you have your walking shoes with you as there is a good deal of walking with stairs intermingled with wooden walkways as you wind your way up through the gorge to the caves. These are not true caves but talus caves the result of glaciation ~13,000 years ago and subsequent rock falls resulting in gaps between large boulders.
In 1852 two brothers Royal and Lyman Jackman stumbled upon the gorge while they were in the area fishing. One of the brothers slipped on a moss covered boulder and fell into a cave in waist deep water. It was the first of a great many cave that they found. In 1912 the area was being threatened by heavy logging so the Society for the Protection of New Hampshire Forests a non-profit organization purchased the land to protect its natural beauty. The society still owns the land today.
From the visitor center make your way to the walkway through the gorge up to the boulder caves.
Once you get to the caves the fun starts, who doesn’t like scrambling around and under big rocks. For some of the tighter squeezes there are bypasses around the caves so you can opt to walk around.