Nara is a former imperial capital of Japan and served as the capital before Kyoto.
While there are many attractions here, the biggest (literally) is the Todaiji Temple, which is the largest wooden building in the world. It makes for a great bookend with Hyruji if you like wooden building superlatives.
You can visit Nara via a day trip from Kyoto, but I think there is enough there to justify at least an overnight stay if possible.