Ah, the walls. There are two of these, and when I did the Mud Run last year I pictured these giant brick 25-foot walls. I mean, I knew they were 6-foot-high (or thereabouts) and made of wood, but they may as well have been unyielding monsters.
They weren't. I scaled them just fine. I guess I'd built them up in my mind to be too tough to get over but they weren't. Now, they weren't tiny hurdles either but they were a good obstacle amidst plenty of obstacles.
Here's a video I find on YouTube that shows one of the walls of the Mud Run. This looks like the second one of the two on the course. The best part about the walls is that you get muddy when jump down, as you'll see on the video.