Bumpass Hell trail is a 1.5 mile hike to Lassen's sulfur works. Elevated at 8,000 feet you get a view like no other. There are perfect spots you can plop on a rock and enjoy the scenery.
About a mile into the hike, you begin to smell the stench of the sulfur holes. You get to enjoy this for another 20 minutes until you actually reach them. The sulfur holes are big pits in the ground spewing out clouds of sulfur gas. There are also a bunch of pools and small creeks of water that are boiling hot. Many pools are literally bubbling from the heat.