Within easy driving from Fresno (about 30 minutes) you can visit the Kings Canyon and Sequoia National Parks (). There is an entry fee of $20 per vehicle, but longer term admission passes are also available.
One of the special attractions in Sequoia National Park is the Boyden Cave. Situated along the Kings Canyon Scenic Byway, The cavern is a limestone cave that was discovered by a fisherman, named Boyden, fishing on the nearby Kings Canyon River. He actually lived there and gave guided tours himself for 5 cents apiece, long ago. The cavern has many interesting formations of stalactites, stalagmites, including – an upside down miniature Disneyland, a wedding cake, a bear, a stack of pancakes etc. and there’s also a subterranean stream that you can follow out. Just outside flows the beautiful Kings Canyon River that you can even walk down to. It’s always 55°F inside the cavern so a pleasant break even on a hot day.
A great way to introduce caves and their many wonders to kids – our 4 year old enjoyed the walk, following the stream back out, an ice cream at the gift shop and then building a cairn by the river.
Regular tours of the cave are given by a licensed guide company (http://kingscanyon-boydencavern.blogspot.com), the walking tour is 45 minutes and costs $14.50 per adult and $8.50 per child. For the more adventurous rappelling and canyoneering are tours also available. The tour guide is knowledgeable and friendly, ours even took a very nice family photo for us on request. Just bear in mind that it is a steep walk from the gift shop to the cavern – so take your time.