Lassen is small (driving its length takes only about an hour), but it's dotted with streams, lakes, and hissing hydrothermal action. All the good stuff feels close and easy: You can take a short hike to some astonishing natural wonder and still have time for a lunch-ruining soft serve at the Manzanita Lake store.
We spend a morning at Bumpass Hell, marveling at the boiling mud and sapphire water. By afternoon, we're back at Summit Lake, splashing in the frigid shallows and snoozing on its warm banks. Two boys we call Huck and Finn paddle lazily in their inflatable raft.
The next day, the 1.5-mile trail to Kings Creek Falls takes us through fawn lilies and towering red firs. We stop to watch a six-point buck grazing in a meadow of wildflowers, and as we stand there, a hawk alights on a branch not 10 feet away. I half-expect Thumper to appear.
The trail, empty of other hikers, lets us out at an impressive tumble of water. It's our second nature-calendar moment in an hour, and we pause to exclaim appropriately. Even the twins seem awed.
We continue on, following the path as it hugs the bank of the stream. It's goal-less hiking now. We've seen the waterfall, we've even gotten a wildlife bonus. Now we walk for the simple pleasures of mountain air, perfect silence, and tired muscles.
But Lassen gets us again. We take a spur to the left and find ourselves on a lip of rock jutting out over what looks like the whole world. It's not a famous spot. It's not even on the map. But we cluster on its edge, looking out at endless forests and rolling mountains, and say again what has by now become our favorite word: Wow.
MORE SECRET PEAKS
Three other mountain ranges with a lot of beauty and darn few people
Where North-central Wyoming
Why they're a secret The slightly taller, flashier Grand Tetons have grabbed all the celebs.
Why they shouldn't be The Big Horns are just as beautiful as the Tetons, and nearby Sheridan is as much fun as Jackson. Find 189,000 acres of wilderness in Bighorn National Forest.
The Kofa Mountains, AZ
Where The Kofa National Wildlife Refuge near Yuma, AZ
Why they're a secret Summer vacation plans rarely call for a trip to one of the most sizzling spots in the West.
Why they shouldn't be They epitomize the stark beauty of the red rock desert and contain one of the few natural palm oases in Arizona (but, yeah, maybe wait until fall to visit). 928/783-7861.
Where Eastern San Diego County, all the way to Mexico
Why they're a secret They tend to be overshadowed by Palomar Mountain and its fancy observatory.
Why they shouldn't be They're close enough to San Diego for a day trip and offer spectacular views over Anza-Borrego Desert State Park. 619/445-6235.
More: 20 perfect summer trips