Avenyn or "Kungsportsavenyn" as it is actually named is the most famous street in Gothenburg. The biggest shopping districts are also close to the street, because there are always a lot of people here. I think it is ok, but it is overrated. Food and coffee places are very expensive here. You can eat open-air in most cafés here, but I would recommend you to go someplace else if you want a nicer view (at least I am not into seeing dirty streets and cars when I eat at a café).
However, when you are in Gothenburg this street is hard to miss. And I do really recommend you taking a stroll there. At the top end you also have a huge building containing the city's art museum. In front of it you have a small market place with the most famous statue in Gothenburg: Poseidon. I do recommend a visit there. The view from the top of the stairs in front of the museum is also nice. You can see almost the whole of "Avenyn".
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