Lassen Volcanic National Park (Timothy Hearsum/Digital Vision/Getty)
Gateway City: Mineral
Size: 106,372.36 acres
Date Founded: 1916
Annual Visitation: 382,274
Busiest Month: July  (89,326)
Least-Crowded Month: February  (5,810)
Fees: $10 per Vehicle, $5 if Entering on Motorcycle, Bicycle, or Foot (7-day pass);
Average Temperature:  Jan 31°F, July 66°F
Average Rainfall: 50.37"

Explore the surface of an active volcano? Have you gone mad? Lassen Peak in northern California is an active volcano that could erupt at any moment. But don't let that prevent you from visiting; seismologists claim they'll detect danger long before you need to worry. Besides, things have been pretty quiet around here since 1921, when the mountain last acted out.

Visible from miles around, 10,457-foot Lassen Peak is the largest volcano of the "plug dome" type, which gains a distinct rounded shape when thick lava cools and plugs its own vent. All four types of the world's volcanoes can be found within the boundaries of Lassen Volcanic National Park; its significance as an active volcanic landscape occasioned its national park designation in 1916.

Lassen enfolds 106,000 acres of forested foothills and volcanic relics just north of where the Sierra Nevada peter out. Snow arrives early and stays late, which accounts for the park being operational just three months of the year. The Lassen Volcanic National Park Main Park Road can open as early as May 10th and as late as mid-July depending on how much snow falls during the winter. This fact along with a location far from any of California's other attractions makes Lassen one of the least crowded of the national parks.

Hike the "Ring of Fire" 
If it's geothermal action—like bubbling mud pots, steaming fumaroles, and boiling water—you're after, plan on hiking the four miles from Bumpass Hell to Cold Boiling Lake and Kings Creek. Ascend 500 feet, only to descend 1,000 feet, for wildflowers galore and a coldwater boiling lake. If it's a more eruptive experience you're seeking, try the five-mile round-trip, steady-grade climb to Lassen Peak's magnificent view. Most of Lassen's walks are day hikes; however, combining trails makes for a more extended volcanic experience.

Take the Slow Lane 
The 35-mile main park road was planned for scenic driving, not as a thruway. The drive loops around three sides of Lassen Peak, starting at the park's southwest entrance. Opportunities abound to park the car and take a short walk to thermal areas like Sulphur Works and Bumpass Hell. Mountain meadows, distant peaks, and wildflowers dot the drive until you reach the Devastated Area, where evidence of the 1915 eruption still persists. Hot Rock, a large granite boulder carried down by the 1915 mudflow that took ages to cool off, and Reflection Lake, offering a perfect reflection of Lassen Peak, mark the end of the road.

Snowshoe, in Black and White 
Where on earth do black Fantastic Lava Beds and cool white snow exist in contrast? Cross-country ski or snowshoe your way to Lake Butte, and at 6,100 feet, you'll find out. The more ambitious explorer will want to make the trek to the secluded Juniper Lake and Warner Valley areas; once the snow falls, these die-hard areas are only accessible by skis or shoes. Be on the lookout for the occasional black bear track: a reminder that not all bears spend the winter months in a deep slumber.

Sled at the Chalet 
Once the snow begins to fall and the main park road closes, the center of action swings to the Chalet and Snow Play Area, which is located a mile beyond the park's southwest entrance. Tobogganing, sledding, tubing, snowboarding, and for those silly enough to do it, winter camping is allowed. The Southwest Walk-In Campground near the Chalet is open year-round. Water and restroom facilities are nearby.

Birdwatch at the Flyway 
It's not uncommon for snow to fall every month of the year in the park's high ground, so smart birds head for low-lying areas, like the mini east-west flyway between the Great Basin and the Sacramento Valley. It's not uncommon to find interesting migrants cruising this flyway. Mineral and Battle Creek meadows experience milder winters and are also common spots for birding, as well as the lower lying lakes, Manzanita and Butte, where habitats merge and varieties of birds can be found feeding and nesting.