The reason Abingdon exists at all is the Benedictine abbey founded in the seventh century, which dominated the town for nearly nine hundred years before Henry VIII's commissioners pulled it down. What survives sits on the eastern edge of the market square: the late-medieval Abbey Gateway with its passage and porter's lodge, and behind it the Checker, an exceptionally rare thirteenth-century counting house with a tall chimney that is one of the oldest surviving examples of domestic chimney-stack architecture in England.
The Unicorn Theatre now occupies the former Long Gallery and stages plays in a medieval roof space, which is worth attending if anything is on. The abbey precinct itself is laid out as a public park called the Abbey Gardens, with informational panels marking where the cloister and church once stood. Entry to the grounds is free.