Though construction work may be typically defined by unions, hard hats, and high-visibility vests in nearly every color imaginable, a whole lot more goes into setting down our infrastructure than what meets the eye. Sometimes, it can even be downright metal, complete with flames, big, scary machines, and hard-as-heck workers to boot.

From a glimpse at what underwater welding is really like to the — literal — heights wind turbine workers have to climb in order to keep our green energy green, here are 16 incredibly heavy metal photos of people and machines at work.