As you continue north past Yellowstone Lake, you enter the Lamar Valley. Here, you will see large herds of bison. With such a food source, it is likely here in this part of the park to see wolves and grizzly bears. When you see large numbers of observers with their spotting scopes and long range lenses out, they are probably tracking one of these predators. As you turn back to the western edge of the park, you will pass through some rocky terrain, where you can possibly see some big horn sheep among the rocks. Also in the northwest corner of the park, are some geothermal features that are worth stopping for, Mammoth Hot Springs Terraces.
Above all, do your research ahead of time on the park’s web site, and enjoy nature!