The most-visited of all of Berlin's museums, but also its most controversial. The altar found at the site in Turkey after which the museum is named, depicting a war between the giants and the Olympian gods, is an unusually intact Greek high-relief frieze, and since the late nineties there have been campaigns by Turkish politicians to return the piece to its land of origin. Any way you look at it, it's a magnificent display of colonial spoils that is not to be missed.