The Studentenkarzer was the student prison of Heidelberg University until 1914.
At that time, the university still had its own jurisdicton, allowing an official to impose Karzer sentences. Depending on the offense, detention lasted betweek three days and four weeks; however, students were allowed to attend their lectures. After university activities, the detainees had to serve their time in the Karzer. Many passed the time by immortalizing themselves on the Karzer walls with portraits and inscriptions. These "artworks" can still be seen today.