It’s a giant sequoia, a member of Sequoiadendron giganteum, one of several surviving species of redwoods. The living crown (this one atop the General Sherman, at center) was once a distant mystery.

In the heart of California, the Sequoia and Kings Canyon National Parks are home to some of the tallest trees on the planet. Here’s how best to explore these other-worldly sites from Visalia, the ...