The house, standing at 16 Chernel Street, dates back to mediaeval times and is also referred to as Old Bastion. The construction was erected in the 14th century and functioned as the southwest bastion of the town wall in times of war. The wall stretched about 10 meters from the outer wall and provided a passage to another bastion (Sarkos-bástya), standing at 12 Chernel Street and also known as the Little Zwinger.

The building had been referred to as Old Bastion up until the 1700s, but from then on residents called it Zwinger. In Europe almost all mediaeval castles had their old bastion. This part of the stronghold was erected in the innermost core of the edifice, it was the part that the army had to defend at all costs even if the rest of the castle had already been taken by the enemy. Old bastions played the same role in castles as citadels in fortified cities: if the castle was captured, the defenders retreated to this tower. These towers were the strongest and tallest units of the castle, at first rectangular, then circular in shape; and they rose above all other defence constructions. When in need, the top section of the tower was possible to be separated from the bastion. As part of the defence function, the bastion had an underground exit leading outside the castle, often outside the town walls. We have no knowledge of such a secret tunnel beneath the Zwinger, but even if such a system existed, it is likely to have been buried over the centuries.These kinds of towers were often used for residential purposes, as well.

Zwinger, located at 16 Chernel Street, is a two-storey edifice with a cellar. The building is known to have had several different functions over the centuries; besides its obvious role as a stronghold, it also served as a place for storing food and other goods and, according to local rumour, it even served as a jail. The cellar and the first floor were used for food storage. Once the tower lost its defensive function, there were several ideas as to what new function it could have: there was one particular suggestion in the 1820s that it could be turned into a theatre. A German troupe under the leadership of Vilmos Flár was staying in Kőszeg at the time, and they were entertaining the idea of establishing a permanent theatre for the town, but this plan never saw the light of day.

The building was finally refurbished in 1965 based on the plans of an Austrian-born architect and Ybl Award holder János Sedlmayr. Today the building belongs to the Institute of Advanced Studies where not only educational activities are carried out but also presentations and exhibitions are held on a regular basis.