Karlovac Fortress (Tvrđava)

Karlovac began as a fortress. Construction started on 13 July 1579, by order of Archduke Charles II of Inner Austria, on the flat ground where the Korana flows into the Kupa, below the older hill fort of Dubovac. The new town was named Karlstadt after the archduke, and it became a key stronghold of the Habsburg Military Frontier against Ottoman expansion. The estates of Inner Austria financed the work, and the plan is credited to the architect Matija Gambon.

The fortress followed the model of an ideal Renaissance town: a six-pointed star with a central square and straight streets crossing at right angles. The fortified town was largely complete by September 1580, and the surrounding moats and earthen ramparts were finished between 1582 and 1589. Locals call the historic core simply the Zvijezda (the Star), and the whole ensemble is protected as a national cultural monument.

Little of the actual fortification survives above ground. What remains is the shape. The ring of former moats can still be traced around the old town, where the ditches have been turned into tree-lined promenades and parks; the name Šanac (trench) still marks part of this belt. Inside the star, the regular grid of streets is intact.

At the centre is Trg bana Josipa Jelačića, the central square of the original fortress plan. On it stand the Franciscan monastery and the Church of the Holy Trinity, whose Baroque bell tower is visible across the old town. Radićeva Street, largely pedestrian, is the main link between the square and the Kupa.

The Karlovac City Museum (Gradski muzej) occupies the oldest mansion in the town, a former Frankopan residence on Strossmayer Square at the edge of the star. It is one of four units of the Karlovac City Museums, together with the Vjekoslav Karas Gallery, the Homeland War Museum at Turanj and Dubovac Castle on the hill above the town. The city tourist board lists the museum building as temporarily closed for renovation, so check before planning a visit around it.

The best way to understand the fortress is on foot: walk the promenades along the old moat line to see the star outline, then cut through the grid to the central square. Dubovac Castle gives a view over the town from above.