Fort Nečven is a medieval Croatian fortress from the 14th century, and one of the most important fortified buildings in Croatia in terms of size and degree of preservation.
The fort and its associated yard cover a square kilometer. It used to be surrounded by high walls made of small, poorly assembled stones combined with lime. The northeast courtyard wall was separated by a deep moat and perhaps a moving (lifting) bridge from the remains of the fortress. The walls were over a meter thick. The steep southern walls reached a height of up to 15 metres and consisted of five floors. The northern side, where the five-storey ancient square tower stands, is now filled with rubble.
On the other side of Krka, opposite from Nečven, are remnants of another old Croatian city, Trošenj (Čučevo). Those cities were previously connected by a bridge (which was destroyed in 1647 during the war between Don Stjepan Sorić and Krajišnici) that connected central Dalmatia with Bukovica and Ravni Kotari. The bridge was supervised and travellers who passed the border between Šubić's and Nelipić's properties were charged a toll.
The First Lords of Nečven-Nelipić were at the height of their power after the collapse of Mladen Šubić II (1322 AD) when they were named as the major force in the Southern Croatian region by Prince Nelipac.
The Turks ruled Nečven from 1522 to 1678 or 1686, apart from a period between 1648 and 1670 during which it was given to Venetian vassals Šibenik and Trogir, and burned down at the orders of Leonardo Foscolo, using the established constructions they found and the mighty wooden bridge over the river Krka. In their time there lived: the Dizdars, the Aghas, the Begs and the Kadijas), which showed a great deal how important the fort and the city was because it was in effect the seat for administrative and judicial power in that area for that time.
By the end of the 18th century, the fortress lost its strategic importance, and it was abandoned and the surrounding villages depopulated.
References:Carlsten is a stone fortress built on the orders of King Carl X of Sweden following the Treaty of Roskilde, 1658 to protect the newly acquired province of Bohuslän from hostile attacks. The site of Marstrand was chosen because of its location and its access to an ice free port. Initially a square stone tower was constructed, but by 1680 it was reconstructed and replaced by a round shaped tower. Successive additions to the fortress were carried out, by the inmates sentenced to hard labour, until 1860 when it was reported finished. The fortress was decommissioned as a permanent defense installation in 1882, but remained in military use until the early 1990s.
The fortress was attacked and sieged twice falling into enemy hands. In 1677 it was conquered by Ulrik Frederick Gyldenløve, the Danish military commander in Norway and in 1719 by the Norwegian Vice-Admiral Tordenskjold. At both occasions the fortress was returned to Swedish control through negotiations and treaties.