Summiting Lassen Peak, the World's Largest Plug Dome

The route covers about 2.5 miles and gains 2,060 feet in total. You don't need any mountaineering experience, and the path is simple to follow, but the steady uphill push is strenuous. Allow two and a half to five hours.

Lassen Peak is the biggest plug dome volcano in the world. A volcano of this type builds up rather than spreading out, because its lava is too stiff to travel far. In 1915, the volcano erupted violently. The blast opened a crater roughly 1,000 feet wide, and ash from it settled more than 200 miles from the mountain. At one point, steam broke apart the peak's plug, and a rushing slide of snowmelt and rock poured down its eastern flank. Lassen is still regarded as an active volcano.

Much of the route is exposed and high, so the park spreads out below you for most of the climb. Look for Lake Helen, whose vivid blue water sits at the foot of the peak, and for Brokeoff Mountain nearby. At the top, panoramic views reach across northern California.

If you would rather see the park from a car, try Highway 89. Over 30 miles, this scenic road crosses the park's western side, and many of its best-known sights lie right along the way.