It really hits you when you leave the tunnel.
We were warned in advance. The tunnel is long, dark and spooky. We're told what might happen at the end will overwhelm us. We've probably been lied to. It can't be what they say it is.
But when we see it, it's no joke. It's hard to fathom, and all you can do is let your jaw drop. When the morning sun lights the valley and mountains and forest, Yosemite must be the loveliest place on Earth.
Yosemite celebrated 125 years as a National Park in October, although Abraham Lincoln signed a bill earlier, in 1864, to protect the Yosemite Valley and neighbouring areas.
The old National Park sits where California nudges Nevada, about five hours' drive east of San Francisco. At nearly every turn the landscape is startling, unbelievable.
Sporadic droughts and the action of wind, rain, snow and fire lend a dynamism to the landscape. Sure, there are more tourists and roads here now than in Lincoln's day, but a view of the park's most celebrated features from Tunnel View lookout is unchanged from that which wowed visitors generations ago.
To the left, El Capitan, 900m high, a granite monolith standing strong after defying glaciers that scoured away softer rock. Across the dark green valley, Half Dome, another park symbol. If it weren't so dry, we'd also be able to see a big waterfall called Bridalveil Falls too, but there's no complaining here.
Yosemite is unsurprisingly popular, and our exuberant guide, Frank, from Extranomical Tours tells us people have to book accommodation in the park a year in advance. The New Jersey-born, Oakland resident lived in Zambia as a young man, and has seen a fair amount of the world, but Yosemite still leaves Frank awestruck.
Our schedule is a busy one, and we get a lot of walking done.
Sentinel Dome, a rock thought to date from the Cretaceous period, the dinosaurs' heyday, makes us feel like strangers in this world, new arrivals on a planet of ancient grey rock and scattered trees that rise bravely from windswept heights.
Plenty of pathways offer peace and quiet. Frank tells us a spot called Taft Point might be worth visiting. We're left to explore on our own, encountering giant sequoia and some of the park's wildlife. An adolescent black bear comes into view beside a walkway. It sits around chewing vegetation. It has a nonchalance verging on condescension. The gawking humans smile and giggle. The bear goes back to the bush.
On the path to Taft Point, trees push against boulders of limitless variety. The light blue sky appears again, the air changes, and a new vastness appears. Taft Point.
V-shaped gashes in the granite offer views to the valley below. Some huge rocks have tumbled down the crevasses, then got stuck, saved from plummeting into the distance. Heading to the edge of the cliff, stepping carefully, crawling - the edges are 300m high - trigger an instant adrenaline rush.
Where's Frank? There's Frank, feet dangling over the edge. He has a youthful exuberance as he sits beside the fissure, atop a giant rock that from a distance resembles stacked pancakes.
When night falls, we head to Yosemite Bug in the small town of Midpines. The Bug is a quirky collection of colourful lodges outside the national park, but still inside Mariposa (which is Spanish for "Butterfly") County. Dubbed a "rustic mountain resort", each of its cabins seems to have a different theme inside - mine is bright, with Picasso-inspired cubist paintings. Local food and beers are served at the Bug's restaurant, and our hosts regale us with stories, including the unfortunate case of a bear fatally mauling a local man just a few months earlier.
In the morning, Frank takes us to a point in the valley well-placed to watch the sunrise. We're close to Stoneman Meadow, and it's a tranquil spot that encourages meditation. It was also the scene of a riot on July 4, 1970, when park rangers tried and failed to disperse a big crowd of hippies who were accused of camping in the area illegally.
On the valley floor, beside a busy swimming pool, a bicycle hire centre provides an enjoyable way to get around Yosemite's bike trails.
It takes a few moments to get used to the fixed-gear bikes with no brakes but there's no rush hour now, and when trails do meet roads, motorists are courteous.
In late summer and early spring, the air is clear, the skies blue, and on a warm day a ride beneath the trees and granite monoliths, over bridges above the rivers, is an unbeatable experience.
Heading out of the valley and back to San Francisco through California's golden rolling hills, one can't help but feel a whole lot more grateful. Yosemite's grandeur makes life's petty, daily struggles inconsequential. There's only one thing to worry about: How do we get back to Yosemite?
Air New Zealand flies up to seven times a week non-stop to San Francisco from Auckland. One-way Economy fares start from $889. airnewzealand.co.nz
This year marks the centenary of the US National Parks service.