As a department of the World Ocean Museum, the Friedrichsburg Gate carries on the maritime theme of its parent organisation with a fascinating (and from time to time hands-on) little exhibition centred on historical ship building and restoration processes. Split between the gate interior, which presents a set of exceptionally well-lit scale models and visual displays, and the adjacent Lodejny Shipyard building, in which you'll find a wide selection of previously recreated/restored light vessels from around Russia and Europe, the mini-complex does an admirable job of bringing the subject to life. At various times there are also live demonstrations of traditional craft techniques and the opportunity to see boats out on the river so it's worth checking their calendar of events in advance.