For no doubt, the Ohara Festival (おはら祭り) is definitely the biggest event in Kagoshima City. It happens every year, on the 2nd & 3rd of November. Citizens of the whole city gather and just dance on the tramway. The festival started in 1949 after the war, to celebrate the 60th anniversary of Kagoshima City. It is the biggest festival in southern Kyushu.
The traffic on those days is mostly stopped or re-routed. It is better you use a bicycle, or just simply walk. Starting from the City Hall to the Tenmonkan shopping area, every where will be flooded with people. So be prepared!
One year, I had joined the group "Genki Gaikokujin and Friends" organised by Kagoshima City Hall's International Relations Coordinator and danced in the middle of the city. It was a very fun and memorable experience of Japanese culture! Even you're just a visitor of the city, you could still join in during the time of "free dance" section with everyone. So don't be shy, let's dance in the festival!
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