The Red Tower was built in the 15th century as a prison in the Southeastern corner of the medieval fortress that surrounded the town of Pärnu. It is the only defensive tower of the Hanseatic town of New-Pärnu that has been preserved. This granite tower got its name from the brick that used to line the inside and outside of the tower. In the 17th century, the tower had four storeys and a prison cell that was 6 metres deep. Three storeys have been preserved.
In the 19th century, the building was renovated into the town archives, but the building served a number of different purposes over the following century.
https://www.visitestonia.com/en/the-red-tower#