Haithabu

"Who is the cleverest Viking of all?
The life of the Vikings was rough and tough, but even they were not able to survive without exchanging goods.
Haithabu-the Venice of the Vikings with its stilts- was founded as a center of trade during the 8th century. Whatever trade flourished, there were jealous people, highway robbers and gangs of robbers. For protection, protective walls, traps and bridge systems were constructed that were supposed to make life difficult for all undesired intruders.
Every year, the inhabitants of Haithabu hold a contest in their town, in honor of Odin, to find out who is the cleverest of all in overcoming the traps."