The Burgkloster is the surviving Dominican monastery at the northern tip of the Altstadt, founded in 1227 and the largest complex of medieval brick monastic architecture in northern Germany. After the Reformation it was used as a workhouse and then a courthouse and prison; the most recent restoration uncovered medieval frescoes hidden under later plaster.
The cloister, the chapter house, and the great refectory are open to visit as part of the European Hansemuseum next door (a combined ticket covers both). The contrast between the medieval architecture and the contemporary museum is one of the strongest design statements in the city.