Lassen Peak The park’s namesake, this peak is the largest plug dome volcano in the world. It rises high above the west side of the park. We had planned to start early to make it to the top by sunrise. But a late start on Sunday (we couldn’t help it), followed by a sleepless night the first night (yes, we slept in the car on the first night on the road) meant we rolled into the trailhead parking lot, fell asleep for an hour, and then started hiking as the sun came up.