Old Lassen Trail has only one trailhead, so you're looking at an in and out backcountry trek. Old Lassen Trail has a total elevation difference of 2,089 feet which is an average number. Of course, this is an overnight walk, 2 days normally, so better have big a backpack to fit all the stuff you need. Being 14 miles long; it's longer than many trails. This is a hiking trail that is quite long, so make sure you bring plenty of supplies. At parts of the year this vicinity sees very little rain, so do check for current fire restrictions before you go if you plan to bring a stove or make a camp fire. Some parts of this trail are much higher up than other parts of the trail, and that means that some parts of the trail could be very different from other parts of it.