This month, extreme endurance athlete Marshall Ulrich and firefighter Dave Heckman finished an unprecedented expedition, going on foot around the perimeter of Death Valley National Park during the hottest part of summer, completely unaided and unassisted. They began on July 22 and concluded 16 days later on August 7.

While others have trekked in this area, no one has attempted to circumnavigate the park, and certainly not during the height of summer when the threat of dehydration and heat stroke are dire. To grasp the gravity of this, consider that on the same day Ulrich and Heckman finished their trek, another accomplished ultrarunner died in Death Valley after just a few hours under the blazing sun.

To survive the scorching 120°+ temperatures and be self-sufficient even as they moved through remote areas, crossed six mountain ranges with a total of about 40,000 feet of elevation gain, and covered approximately 425 miles, the men had buried water, food, and supplies along their route two months earlier. Nearly all of the 37 caches were intact; in one, the water had leaked out, and a few were invaded by insects, but none of this created a shortage and they had enough water and food to sustain them throughout the journey.