n the isthmus between Lake Biskupińskie and Lake Venetian before 1383, Mikołaj Nałęcz of Chomiąża erected a castle on a square plan with a side of 33.5 meters with a tower in the north-eastern corner and a residential building along the western wall. The entrance through the fortified foregate protruding in front of the face of the walls led in the southern curtain of the walls. Mikołaj Nałęcz called the Devil of Venice, having his support in the erected fortress, became a dangerous adventurer exploiting the local population.
The castle was damaged in 1395 during the siege by the Grzymalites. After the death of Mikołaj in 1400, it became the property of his son-in-law from the Pomian family from Warzymów. Between 1411 and 1420 there was a fire in the castle, after which Mikołaj Pomian sold the property to the archbishop of Gniezno, Mikołaj Trąba. Before 1436, Mikołaj Trąba or his successors enlarged the complex, surrounding it with the second perimeter of the walls protruding in front of the original one by about 5 meters. On the corners of the second wall there were small bastions adapted to artillery fire. Also during this reconstruction, the residential building was enlarged by a chapel. It is possible that the castle was also adapted to imprison priests who exposed themselves to the church authority.
At the end of the
View from the East Tower, photo by ZeroJeden, V 2005
15th century, Archbishop Jakub of Sienno, in connection with the reform of the bishopric key of Żnin, issued an order to demolish the Venetian castle. The material from the demolition carried out in the years 1479-1480 served as a building material for the new residence of the archbishops in Żnin.
For centuries, nothing changed for the better, the passage of time leveled the faint remains of the walls. Among the rubble rubble, there was still a square tower from the north-eastern corner, preserved up to several meters high. It was not until 1968 that Czesław Sikorski began to examine the relics of the fortress covered with earth, the research was related to the works uncovering and securing the remains of the walls as a permanent ruin.