One of the ways to search for the largest folder/directory in your computer is to use the du command. du is used to display disk usage statistics, in this case we will use du to get a list of all the folders in the order from the smallest to the largest. Using this command du -S | sort -n this process will take some time, depending on your harddrive size and how much content it has. In my case it took a solid 5 minutes.
Check out the du man page for more info on du: http://www.hmug.org/man/1/du.php