Bastion of St. Rocha was erected in the years 1631-36 by Jan Zywerth, a bricklayer, as one of the four huge, polygonal bastions, according to the design of the outstanding military engineer and architect Andrea dell'Aqua (who, by the way, is the creator of the entire fortification). These buildings managed to withstand the famous siege during the Swedish Deluge in 1655. War technology, however, advanced quite quickly, which meant that from 1674 the stronghold was again modernized according to the designs of the outstanding Polish military engineer, Krzysztof Mieroszewski. These works lasted until the middle of the 18th century. During renovation works in the early 1690s, fragments of fortifications from 1631-36 were uncovered, together with walls remembering the times of the Swedish siege of 1655 and bearing traces of cannonballs of that time. The restored interiors of the bastion were intended for museum purposes. In 2006, the first part of the permanent exhibition was officially opened, entitled "Bogurodzica. Splendor of the Polish-Lithuanian Commonwealth”. It includes artefacts from the end of the 18th century, including military items and valuable oriental products, e.g. trophies of the Battle of Vienna, once donated to the monastery by the family of King Jan III Sobieski. The upcoming part of the exhibition is to illustrate the history of the struggle and martyrdom of Poles during the partitions and in the 20th century. Temporary exhibitions are also organized here.