But there are walking tours led by National Park Service rangers that explain how these huge chunks of granite came to be. They're not just the result of erosion, but were also formed by melting glaciers and forces under the ground that over the millions of years pushed them higher and higher. It's a way to understand the massive forces that formed the Earth itself.

Visitors can also follow the footsteps of famed photographer Ansel Adams, who made his home here for a quarter century. You can even snap your own pictures from where Adams stood when he took some of his most iconic photographs. Classes cost about $100 but the Ansel Adams Gallery also offers free camera walks on certain days (tours fill up; reserve ahead).

Getting there

Getting there can be a challenge on roads that are potentially snowy and icy. Car rental places may tell you－as they told me－that snow chains aren't necessary. They are, to be blunt, lying.

"California law says if you are entering a chain-control area, you have to carry chains," says Scott Gediman, a park ranger and a public affairs officer in Yosemite. "Everybody needs to have chains, even if you have four-wheel drive."

Rangers don't enjoy checking car trunks for chains and cables but they do it and they will send you out of the park if you don't have them.

The good news is that chains are not that expensive, costing as little as about $40, and can be purchased at any auto supply store nearby.

Snow-chain technology has improved dramatically, making it far easier to put the chains on than it used to be. But if you still feel like you can't do it, there are services along the road that will put the chains on for you for $30 or so.

Yosemite Valley is about 338 kilometers from San Francisco. But if the winter drive sounds intimidating, use the YARTS bus service which runs year-round between Yosemite and Merced, a city located about 210 km from San Francisco.

ASSOCIATED PRESS