This is the world's largest vacuum chamber - a gigantic 122 foot high aluminum cage designed to simulate the airless environment of space.
NASA uses it to test spaceship prototypes and create giant marshmallows. (One of those statements is a lie.) In addition to vacuum, it can heat or cool the environment from -260 to 175 degrees Fahrenheit (111 to 353 Kelvin).
I wouldn't want to have to replace the o-ring on that sucker!