I did the Tough Mudder at Beaver Creek, CO. 12+ miles at 12k+ feet elevation. Up and down ski runs. It's not nearly as fun as it sounds. Yeah that was an a$$ kicker.
The worst obstacle for me was the alpine ponds. The water was 35-40 degrees. The first pond was ok. It was about 30 meters wide and only waist/chest deep. The second pond couldn't be waded. They also placed 3 rows of barrels across the pond so you had to swim under water. I physically couldn't take in a breath after the second row. It was brutal.
The worst obstacle for me was the alpine ponds. The water was 35-40 degrees. The first pond was ok. It was about 30 meters wide and only waist/chest deep. The second pond couldn't be waded. They also placed 3 rows of barrels across the pond so you had to swim under water. I physically couldn't take in a breath after the second row. It was brutal.