Marienburg Harbour is a Special port building in Total War: Warhammer. The greater harbour of Marienburg lies past the Manannspoort Sea, just beyond Rijker's Isle.
Marienburg sits on a delta at the mouth of the Reik as it heads through the cursed marshes and eventually into the Sea of Claws. The city is on a series of marshy islands surrounded by quays and docks, making its populace rich due to the trade income generated. They are so wealthy, in fact, that they bribed themselves out of the Empire in 2429 IC!