The Lotrščak Tower is located in an old part of town called Gradec of Zagreb. The tower, which dates to the 13th century, was built to guard the southern gate of the Gradec town wall. The name is derived from Latin campana latrunculorum, meaning 'thieves' bell', referring to a bell hung in the tower in 1646 to signal the closing of the town gates.
The Grič cannon is one of the Zagreb landmarks. In the 19th century, a fourth floor and windows were added to the tower and a cannon was placed on the top. Since 1 January 1877, the cannon is fired from the tower on Grič to mark midday. The cannon was to give the sign for exact noon for the bell-ringers of the city's churches.
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.