The Barbican was built at the end of 15th century (1498-1499) and it was the strongest element of the expanded fortifications in Kraków. In the manuscript of Baltazar Bohem, there is an entry suggesting that the cornerstone was laid by the Polish king Jan Olbracht. Olbracht's involvement with the project and its progress is quite visible as he did not stint funds for the investment. Time was of the essence, as Poland was threatened by invasions of Wallachian, Tartarian and Turkish hordes whose plundering expeditions reached the borders of Małopolska.
The Barbican is an unusual monument of defense architecture. It's an architectural design of a circle, ratio 6:10. Formerly, it was connected to Floriańska Gate with a neck. Its internal diameter was 24,4m and the external was 30m. It was surrounded by semicircular, 26m wide and up to 6m deep moat. The moat was filled up, as the city expanded. In the underground part of the building there was a vaulted pass. It led to the gates, which allowed the crew to get pass the moat and escape the fortress.
That pass consisted of two parts, western was more than 10.5m, eastern exceeded 12.5m.
The walls of the Barbican were very solidly constructed thus a good example of very skillful engineering which is exemplified here by usage of limestone. Up to the moat surface, walls were made of limestone.
Lime mortar was used to join the stones. The structure above the moat surface was made of kiln-fired bricks.
The wall was artillery fire proof, its thickness ranged from 45cm to 3m. It was a solid protection for the fortress crew.
The Barbican has four loop-holed storeys, grid distributed. They were especially constructed for light firearms. The loop-holes numbered up to 130. The loop-holes were spread apart adequately enough to allow for wide area of coverage with gunfire. Since 1566, major function of the Barbican was for defense of the Armory (build in 1565 by city architect Gabriel Słoński).
Building's facade is crowned with machicolation; it also includes a forwarded balcony with floor hatch that was used to pour melted lead, boiling oil or to throw projectiles. The crowning element of machicolation piece was seven observation towers--octagonal and circular, and they could only be reached with ladders.
One of the city's major gates was inside the Barbican, facing towards Kleparz, 30 deg west from Floriańska Gate passage. In the past, it led to a drawbridge over the moat, which was supported on the base of brick-stone pillars.
Barbican was situated next to the Droga Królewska (Royal Tract). It routed from collegiate church of St. Florian, through Barbican , Brama Floriańska (the Floriańska Gate), Flosiańska Street, Main Market Square next to Marian's Church, Grodzka Street, Senacka Street, Kanonicza Street, as far as Wawel Hill. It was the main route of coronation marches, funeral processions for Polish kings, and a visiting route for important European diplomats and members of the royal families.
Throughout history Barbican entrance saw many national heroes and leaders being warmly welcomed by citizens of Kraków. It became known as the Porta Gloriae (Glorious Gate) of Kraków. Entrance of the King through its gates also traditionally symbolized takeover of authority over the capitol.
Barbican was a fortress almost impossible to conquer. Its first test came in 1587 in the battle for the Polish Crown. Kraków's city walls were surrounded by the army of archduke Maksymilian--the royal line of Habsburg. The Attack of his troops was repelled. The pretendant to the throne was forced to leave the city. Another important trial took place during the siege by the Swedish Army-(commonly referred to as "Potop Szwedzki" in polish history) in 1655. The troops defending Barbican had only surrendered because of the lack of ammunition and starvation. In 1768, during Bar Confederation Barbican was used to fight Russian forces.
The beginning of the 19th century initiated start of the battle for Barbican 's survival. Following the imperial decree of Francis II in 1806, disposal of Kraków's medieval city walls was begun. With a careful effort of an architect, chief conservator and Senator Feliks Radwański, in 1817 Barbican and northern part of walls was saved. That was a landmark decision in Barbican 's history. The medieval defense fortress became a monument of art and fortification. Today Barbican falls under the jurisdiction of the Museum of History in Kraków which has made it accessible for the tourists, who can tour its interior with outline of historical development of fortifications in Kraków.