The Italian architect Giovanni Morando Visconti has made the project of the fortress. He was guided by the general Stefan de Steinville and later by general Weiss. The work at the fortification of Alba Iulia has began on the 4th of November 1715, when the foundation of Carol bulwark, dedicated to the emperor and situated on the Northern side was made. Weiss named his project, the fortification, "Alba Iulia's major fortress in the Principality of Transylvania".
Between the 18th and 19th centuries the fortress has served as the military center of Transylvania and also as general armament dump. The perimeter of the walls is about 12 km; 20.000 serves built the walls.
The fortress has seven bulwarks (Eugene of Savoia, St. Stefan, The Trinity, St. Michael, St. Carol, St. Capistrano and St. Elisabeth) that make it a star shaped one, common to Vauban fortresses. The biggest bulwark is the Trinity one, measuring 116 and 135 m and being decorated in the center with a blazon crowned by outlines and acanthus leaves.
The walls were made of bricks, quarry stones, or out of the Roman ruins, measuring 3 m at the base and 1.20 m at the top, being sustained by abutments in order to neutralize the earth's force. The six gates of the bulwark fortress have been a model for the 18th century Transylvanian architecture. They are looked upon as extremely valuable samples of early baroque.
The planning and the building of the fortress led to the modification of the street texture; that is why the six gates had been placed three towards the town and the other three towards the western drill field. All the roads and the fitted gates were functional. The fortress is outstanding both for its decorative elements and for the beauty of its six gates, unique in European military architecture. Doubtless the artists had been inspired by ancient mythology. Sculptors like Johann Koning, Johan Vischer and Giuseppe Tencalla had made the decorations. On the whole, the fortress stands out as the most important baroque figurative plastic pile.