The view at the Red Crater alone is enough to make the Alpine Crossing or one of the multi-day hikes worthwhile. However, it should be taken to bring along warm clothes because it can be very cold and windy up there.
Most people take a break when they reach Red Crater. Just walk a few extra meters to the top and you'll be rewarded with a wonderful picnic place from where you can see the Emerald Lakes too.
If you come up the path, you stand relatively suddenly on the edge of the crater and can only be amazed. An unbelievable view of the crater and of a vent!