A dramatic time-lapse video showing the scale of the work carried out by engineers on the new San Francisco Bay Bridge over a weekend closure.

To divert traffic onto a temporary bypass viaduct, making way for the completion of the new East Span, a 300 foot, 3,200-ton section of the existing San Francisco-Oakland Bay Bridge was rolled aside and replaced over Labor Day weekend, 2009. This video presents the entire weekend twice, as seen from above and below.

Video courtesy of the Metropolitan Transportation Commission.