When you think of building railroads, you probably think of old-timey tough guys with massive hammers, beating in the huge metal stakes as they made their way across the country.

Well, the times, they are a changin'.

These days, massive machines -- like the one in the video below -- do the dirty work of laying down train tracks.

The coolest part about this thing is it rides on the train tracks it is replacing at the same time.

Free Beer estimates this train is "about 500 miles long and weighs a million tons." That seems pretty accurate.

Source: Free Beer & Hot Wings