If you are visiting Kairakuen Park by train, get off at Mito station. From the station, turn right to the bus station, and take the bus in front of the Lawson convenience store. I got off near Lake Senba and walked to the bridge leading into Kairakuen. The bus takes about 15 minutes and is 230 yen. Located in Mito, Ibaraki, it was built by Nariaki Tokugawa, the 9th lord of Mito. The name Kairaku means "to share pleasures with people".
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Find out more about Kairakuen Garden.