Lübeck is the oldest port in Germany located at the mouth of the river Trave into the Baltic. In the Middle Ages – as the most important port on the Baltic Sea – it served the function of the capital of the Hanseatic League, the confederation of merchant cities. The most beautiful sights of the city come from the time of its heyday, these include Gothic churches and tenement houses, as well as Renaissance merchants' houses. The old town of Lübeck is located on an island surrounded by the river Trave and the Elbe-Lübeck Canal. The streets above the waterways were the first choice for the location of merchant houses. This was due to the fact that merchants' mansions housed not only their apartments, but also warehouses and the office facilities, where transactions were concluded.