The Tartu Student Lock-Up (Kartseri) is one of the more unusual attractions in Estonia — a small jail in the attic of the university's main building, used from 1820 to 1895 to confine misbehaving students. The walls are covered in over a century of student graffiti: names, dates, drawings, verses in Estonian, German, and Latin, and the occasional philosophical observation from someone who had nothing better to do.
Access is via a guided tour of the university main building, which also includes the restored lecture hall and the university art museum. The lock-up itself is tiny — a few cells with narrow windows — and the graffiti is dense and surprisingly legible once you start reading it. One of Tartu's more memorable half-hours.