After Lassen Peak, the 3 mile round trip Bumpass Hell hike is possibly the park's most popular trail. The trail is named for an early settler, Kendall Vanhook Bumpass, who fell into a boiling pool and severely burned his leg. The leg was eventually amputated. The trail offers great views on the way to the largest hydrothermal area in the park. Once you reach the basin there is a boardwalk through the thermally active area to safely give you a closer view of mudpots and fumeroles. To get another perspective of the basin, head up the Cold Boiling Lake trail. This trail is in the basin and starts just before you reach the boardwalk. Even if you don't want to go all the way to the lake, head up the trail to higher ground. From there you can get a wider view of the basin. The parks website has a good trail guide and video for this hike.