On my first weekend here in Ibaraki me and another intern went to Mito. One of the most interesting sights there was the Kōdōkan, which was formerly the location of the Mito Clan School, and is now a museum that tells of its history. It costs ￥400 to get in and it closes at 4:30pm.
If you can read Japanese, then you can find out a lot about local history. But you can also check out this website for more information: https://www.japan-guide.com/e/e6204.html
On the outside, there were lots of flowering trees. We went there in January, so the only the camellias were in bloom, but it would definitely be very beautiful in spring.
Afterwards, we went to the nearby Kashima Jinja (not to be confused with Kashima Jingū) and Hakke-dō and the attendant at the shrine kindly talked to us about the history of the two buildings.
We had lunch at a ramen restaurant in Mito station, and then also saw Lake Semba. Unfortunately, we didn’t have time to see the garden called Kairakuen, which is on the opposite side of the lake from Mito station, but other interns may want to check it out.