In 1825 Jan Mallet-Malletski designed a strange fortification structure in the left, northern flank of Bastion I called “defensive

traverse”. It was a two-storey, thick-walled casemate building which ended curtain wall I-VII an whose back fitted into the embankment. The main purpose of the building was to defend the inside of the bastion using light artillery as if Russians were afraid that Bastion I might be the target of a particularly fierce enemy attack. The reason why Bastion I was equipped with this additional and expensive defensive structure is still a mystery. It did not take over the function of an earthen retrenchment visible in 18th century plans of the fortifications but was such a unique facility that it was painted two times by Jan Paweł Lelewel. No distinct trace of the defensive traverse has been preserved. At the site of underground remains of this mysterious building there is a small board devoted to the beginnings of a new era in Zamość fortifications as the traverse in Bastion I belonged to the new system of polygonal fortifications. .