I usually only post pure LEGO techniques, but when they are these good, I just couldn't not share it.
This technique by Aaron Dayman, who uses 4L bars as well as the external piece, a BrickArms grenade launcher to create the stunning bridge,
For those of you who don't know, BrickArms sell custom LEGO weapons and other accessories. Although they are not made by LEGO, they are widely accepted in the LEGO community as it is not a fake brand stealing ideas for LEGO themselves.
This bridge looks so great because the grenade launcher piece spaces the 4L bars out at the perfect distance. You can also achieve a slight flex in the bridge, adding to its aesthetics.
Check out Aaron's post on Flickr here: https://www.flickr.com/photos/cbla_member/3502803765/in/gallery-37217189@N04-72157633532233362/