It benefits from the fact that the Mstov River has delta of marsh and fen that limits the size of vessels navigating through it. Ships coming down the Mstov will often sail the coast to Demmen to offload their cargoes, which are then shipped on larger vessels capable of handling the winds and waves of Woden's Sea and farther.
Its defenses are not minimal, but they have not been maintained well. Nor have they been extended as the city has grown to the south. Much of the city is outside its walls, including Southdocks.