Cuxhaven is located directly at the mouth of the Elbe River where it flows into the North Sea and is strongly characterized by its port, fishing industry, seaside resort, and international shipping. The city has only a limited historic downtown; older buildings are found primarily in Ritzebüttel, home to the medieval Ritzebüttel Castle. The cityscape developed primarily in the 19th and 20th centuries with brick buildings, port facilities, villas, hotels, and later vacation homes. Cuxhaven is of particular importance due to its location on the Elbe, a major international shipping route: Virtually all international shipping traffic to and from Hamburg passes through the city. The Kugelbake, which marks the transition from the Elbe to the North Sea, is a landmark of this location.