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:Bomarsund fortress and garrison was built in 1832-1854 by Russian Empire to defence Åland Islands against enemies. British and French fleet attacked against it during the Crimean War in 1854. After a week of fighting the British stormed the remaining fort. Anglo-French forces destroyed it totally after battle. In the Treaty of Paris 1856, the entire Åland Islands were demilitarized, which is a status that has been preserved until this day.
Nowadays there are some ruins left and fortress area is open for visitors.