Michael Wesely - ultra long exposure

This is one of Michael Wesely's ultra long exposure photographs. The photo took 2 years to create and shows new structures being built over time next to the old buildings! The photo shows that the cranes were there for quite a long time as they are bold and clear in the photo unlike the new building that has not been there for long so it appears see through/ ghost like.
I found this photograph on this website which contains a lot of Michael Wesely's work:
http://www.itchyi.co.uk/thelatest/2010/7/20/the-longest-photographic-exposures-in-history.html