A must see. Go to the lodge, drive around the rim. If you have time go on one of the many hikes. You can even hike down to the lake and swim in it, or hike up to a lookout on a peak overlooking the lake (two things I haven’t done yet, but plan to soon). Last year we took a drive out to see the volcanic spires, which are interesting. There’s a first come first serve campsite out by those. In winter you can snowshoe or cross country ski around the rim.