The Stele Forest (Beilin Museum) houses over 3,000 inscribed stones gathered from across China since 1090, displayed in a series of vaulted halls that began life as a Confucian temple. The "forest" is just stone tablets standing in rows, but the writing on them is the actual record of Chinese civilisation — calligraphy by Tang masters, Confucian classics carved during the 8th century to settle scholarly disputes, the Nestorian Stele documenting early Christianity in China, and dragon-incised stones from imperial tombs.
You don't need to read Chinese to find it interesting. The stones themselves are beautiful, and several rooms display rubbings — paper impressions taken from the stones — that show how scholars and printers used these tablets as the master copies of texts for nearly a millennium. Allow two hours. The museum sits inside the old city walls, a short walk south from the Bell Tower along Shuyuanmen, a cobbled lane lined with brush, ink, and seal shops.