 In contrast to a moated castle, with a marsh castle, an area of marsh or bog was used or incorporated as an obstacle to the approach.Marsh castles were mostly built on mounds within these landscapes, in a similar way to a Wallburg.In some places, however, an adjacent area of marsh or bog was simply used for protection on one or more sides and the castle itself was built on solid land, as was the case with the first castle in Danzig (modern Gdansk), for example.