Waldspirale a.k.a forest spiral building in Germany

This is a residential building situated in the Darmstadt, Germany. The unique thing about the building is it has more than 1000 windows and no two windows are identical. The building has total of 12 floors and the building has green roof which means the entire roof is planted with vegetation. This is one of the splendid and unusual buildings in the world and always takes place in the list of strange buildings.