The Ibaraki Prefectural Museum of History sits adjacent to Kairakuen garden and contains an excellent collection of artefacts from Ibaraki's prehistoric, ancient, medieval, and modern periods. The exhibition covers the full sweep of regional history from the Jomon period through the Tokugawa era, with particular emphasis on the Mito domain and its intellectual traditions.
The collection includes samurai armour, ceramics, documents from the Mito Tokugawa archives, and archaeological finds from sites across the prefecture. The building itself is a dignified 1960s structure that fits comfortably into the garden setting. Allow an hour or two, more if you can read Japanese — the written material is substantive.