This was a penitentiary with a circular design that allowed warders to watch inmates at all times.

It was built in 1734 (replacing a 15th-century building) to an unusual, largely circular design.

Most were built to a similar circular design with a roof terrace protected by machicolations.

After extensive renovation that was finished in 2006, the station features a modern circular design, the first of its kind in the world.

In the interior of the ruins are several remains of residences, of a circular design, excavated by recent archaeologists.