These two amazing vintage photographs from 1906 show the Williamsburg Bridge Plaza on the Brooklyn side of the Williamsburg Bridge.
In them you can see the old trollies that used to run across the bridge multiple times a day. The Manhattan-side trolly plaza is now sitting empty and is the space proposed by the Low Line underground park.
These images were obtained from the Library of Congress and are in the Public Domain. More information, as well high-resolution scans of the original glass plates, can be found on their specimen page.