The photo below was taken over almost 14 months at the Leipziger Platz in Berlin - which at the time together with the Potsdamer Platz formed one of the biggest construction sites in the world.
http://www.itchyi.co.uk/thelatest/2010/7/20/the-longest-photographic-exposures-in-history.html
http://www.wesely.org/wesely/index.php#