At the turn of the 16th and 17th centuries Zamosc was one of the most modern fortresses in the Republic of Poland. The town was surrounded with mighty fortifications consisting of defensive curtain walls and bastions and a moat. The topographical elements of the site also increased the defensive strength of Zamosc fortress: the town was built upon the Labunka River and its tributary the Topornica River and was surrounded with a large boggy valley. Zamosc fortification system was designed and built by an Italian architect Bernardo Mornado.
Combining the owner’s residence with the town proper and the topographical features of the site resulted in creating an irregular heptagon consisting of 7 curtain wall sections and 7 bastions located at their bends. Jan Zamoyski – the founder of the new town attached a great importance to its defensive function since the area where the town was built was often threatened with Tatar invasions. In the foundation charter he undertook to protect the town by means of embankments and a moat. During enemies’ attacks the mighty fortress provided the people living in its vicinity with effective shelter. Fortification work was started at the beginning of the 17th century by establishing the perimeter of the town, which measures 2.5 km. Next, the moat was dug up and the obtained material was used for making the embankments of curtain walls and bastions. From 1593 the already existing earth embankments were covered with a slightly sloping wall crowned with a cordon roll to prevent an attack in which ladders were used. The upper part of the wall together with the earth embankment constituted a sloping parapet providing a shooting bench for defenders with 2 m protection. Below the parapet and along the embankment a road was made. On the outside the wall was protected by mighty buttresses hidden in the embankment and joined together by means of vaults. The thickness of the wall and embankment at the very base was almost 7 m. In spite of the fact that the scope of fortification work was very wide, no defensive embankments were made on the outskirts of the fortress. It took 36 years (from 1582 till 1618) to complete the construction of the defensive system of the fortress started by Bernardo Morando. The construction of the fortification system was finally completed in 1618 under the reign of the 2nd entailer, Tomasz Zamoyski. Like other aristocratic families in Poland the Zamoyski family had private troops used for defending the town, the Entail or, if the whole country was in danger, for supporting crown troops.