The Studentenkarzer was the student prison of Heidelberg University until 1914.
The Studentenkarzer (students' prison) is located at the back of the Old University in Augustinergasse. Here, from 1778 to 1914, students were punished for "peccadilloes" (meaning minor transgressions which were kind of fashionable among otherwise honourable gentlemen inscribed at the Heidelberg University, most of them being members of student fraternities) such as violent mensuration, nocturnal disturbances of the peace, or other violations of public order - often they were humid and merry pranks.
At that time, the university still had its own jurisdiction, so a bailiff could impose carceral punishments. The detention lasted between three days and four weeks, depending on the offense, but the students were allowed to attend their lectures. After university sessions, prisoners had to serve their time in the Karzer. Many passed the time by immortalizing themselves on the walls with their likenesses and sayings. These "works of art" can still be seen today.