A thick hemp rope, a system of blocks and two wooden turnstiles moved by... walking workers. The crane’s medieval mechanism lifting 4-ton loads to a height of 11 metres was also used to install masts. Located on the Motława River, Gdańsk’s most characteristic monument is the largest medieval port crane in Europe and at the same time a fortified water gate with two huge brick towers, once protecting the city from the side of the harbour. Now the majestic Crane, as a great example of historic port buildings, a witness of the powerful Hanseatic Gdańsk, called the granary of Europe, is the perfect setting for exhibitions of the National Maritime Museum. Its headquarters are also situated on the other side of the Motława River on Ołowianka Island.
http://visitgdansk.com/en/hity-gdanska/The-Crane,a,3485