This morning we left camp and headed toward the Grand Canyon of the Yellowstone, passing the Heyden Valley on the way, where we'd read was a good place to see wildlife. Uh, yep.

Pics attached show some of the herd of bison we saw, including one performing an odd ritual of barrel rolls, which we captured on camera and video.

Later we took a hike along the south rim of the Grand Canyon of Yellowstone, which was pretty impressive, and had some nice falls running through it. Also on our hike, we saw a fairly remote mudpot, which wasone of the most unique things we'd seen yet. After that, we entered a large field and started seeing lots of bison patties, and then we came around a bend and a huge bison was just sitting in the trail.

• Overlook for lunch.Swatting bugs and sounding like Frankenstein

After lunch we went to see the Petrified Tree, which was the result of lava flows that turned a large redwood tree to stone, yet left it standing upright. On the drive back to the campground, we noticed tons of people everywhere - park apparently filling up. Surprisingly, despite being the 4th of July, we really hadn't felt like the place was too packed until Friday afternoon.

As we turned a corner, we saw a ton of cars on the side of the road. We stopped and saw a grizzly bear and cub (Apparently there used to be two Cubs, but this Cub and the other Cub had gotten into a fight, and the Cub that lost the fight was traded to the San Diego Zoo.)

Having seen a bear, we had pretty much seen everything we hoped to see, except, as Bethany said "an animal in the road". We only had to wait about another ten minutes before traffic was backed up as the herd of bison we'd seen earlier had decided to cross the road. As we sat in traffic, snapping pictures, it started to hail, which only added another surreal aspect to the scene. Our last couple pictures of the day are of the Mud Volcano and Dragon Mouth Cave, which we saw a few miles down the road before the hailstorm caught up with us again.