Murinsel, an island on the river Mur, is a curious and dramatic floating island about fifty meters long with two gateways connected to the riverbank. It is was built in 2003 for the cultural capital of the city of Graz and serves as an amphitheater, a resting place or you can have a drink in the cafe there. I recommend visiting this structure 100%. Although coffee is slightly more expensive than in other pubs of the area, you really should pay the extra. It's a priceless experience.