There’s a big blank spot on the map of the Denver metro.
In the city’s northeast corner, the grid ends abruptly in an open prairie. Instead of cars and trucks, a herd of bison lumbers across the grass. Bald eagles perch in tall cottonwood trees, taking in the panoramic view of downtown Denver on the horizon.
This is the Rocky Mountain Arsenal National Wildlife Refuge, 15,000 acres of open space within one of the fastest-growing metro areas in the country. The land was first set aside by the Department of Defense during World War II for testing chemical weapons. Humans had to steer clear, but animals—deer, coyotes, hawks, owls, and prairie dogs—found refuge here as the area outside the military zone was paved over.