Photos

A typical alley in the Hanseatic-City of Luebeck in Northern Germany.

The Hanseatic League (German: die Hanse) consisted of an alliance of trading cities that established and maintained a trade monopoly over the Baltic Sea and most of Northern Europe for a time in the later Middle Ages and the Early Modern period, between the 13th and 17th centuries.Historians generally trace the origins of the League to the foundation of the town of Luebeck, established in 1158/1159.(excerpted wickipedia.de)

Many of the buildings you see here are from the original founding of the city. In those days civil engineering technologies could not provide materials stiff enough to prevent buildings (non-castle), taller than 3 stories and with thin walls, from toppling over. So they used these "bridges" to lean against other buildings.