The latest Croatian site (2017) to be awarded World Heritage status is in two places: Zadar and Sibenik. Zadar's walls and Sibenik's St Nikola Fort are part of a defensive system designed to protect the sea routes that were central to Venice's economic power back when La Serenissima ruled the Adriatic. In addition to Zadar and Sibenik, the other sites on the Unesco list are: Kotor, Montenegro; Bergamo, Garda and Palmanova in Italy.
Throughout the 16th and 17th centuries Venetian engineers constructed land (Stato da Terra) and sea (Stato da Mar) fortifications throughout Italy, Montenegro and Croatia in a new style (alla moderna) made necessary by the introduction of gunpowder. Gone was the old style of square towers and high walls. In came the new style that emphasized pentagonal bastions, low walls and moats. Alla moderna style cemented Venice's power and was widely imitated in defensive architecture throughout Europe.
From its purchase in 1409 until the fall of Venice in 1797, Zadar was the most important administrative centre and naval base in the entire empire outside of Venice. With a prime position on the Adriatic, Zadar had become a vital centre of maritime trade and was integral to the military defense of the empire. With attacks by Ottoman Turks on the rise, Venice spared no expense in bolstering the defenses of its prized port. The richly decorated gates, imposing bastions and sturdy walls were innovative at the time and remain starkly beautiful.
Sibenik was also important to Venice, primarily for its agricultural products and its salt. In 1468, the Turks launched a devastating attack on Sibenik which prompted the Venetians to reconsider the town's defenses. A number of fortresses were built in and around the town to protect against a land attack. To deter a naval attack the stand-alone St Nikola fortress with its unique triangular design was constructed at the entrance to Sibenik bay in 1547. Positioned at the entrance to St Anthony channel, this imposing fort kept Sibenik town and its vital salt pans nearly impregnable from the sea. It is the only stand-alone fort in the entire Stato da Mar system.