Walls of Dubrovnik

Where it sits. The walls draw a closed ring roughly 1,940 metres long around the old town of Dubrovnik, on a limestone shelf at the southern end of the Croatian coast where the Dinaric mountains fall almost straight into the Adriatic. The landward stretch, facing the slope of Srđ, is the heavy one: up to about 25 metres tall and four to six metres thick, with a second, lower line of defence in front of it. The seaward stretch, standing directly on the rock above the water, is thinner, between roughly one and a half and three metres, because an attacker could never bring siege engines to bear there. The ring encloses only about thirteen hectares, which is why a full lap gives the odd sensation of circling a small town in the time it takes to watch a film.

Why they were built this heavily. The Republic of Ragusa was a merchant state with almost no army and a great deal to lose, so it bought safety with diplomacy, tribute and masonry. Fortification became urgent after Constantinople fell in 1453 and the Ottoman frontier moved to the mountains behind the city. The Florentine architect Michelozzo Michelozzi was engaged from 1461 to modernise the defences for gunpowder, and the great round bastion of Bokar on the western corner is essentially his: a casemated artillery tower designed to sweep the bridge and the little bay at Pile. He also began the reshaping of Minčeta, the tower on the highest, most vulnerable north-western angle, where an earlier square fort of 1319 was rebuilt as a round drum; the sculptor-architect Juraj Dalmatinac finished it in the mid-1460s and gave it the crown of battlements that now reads as the city's signature. On the eastern side, Revelin was rebuilt to a design by Antonio Ferramolino and took eleven years to 1549, during which the Republic banned nearly all other building work so the money and masons went to one place. No hostile army ever took the circuit by force.

On screen. From the second season of Game of Thrones, this ring of stone became the outer skin of King's Landing, and it is the single most recognisable Croatian location in the series. The production used the walls for what they genuinely are — a working defensive circuit with real parapets, real gun ports and a real drop to the sea — rather than trying to disguise them.

• Minčeta Tower, filmed from below, is the exterior of the House of the Undying in Qarth in the second-season finale, the blank spiralling wall Daenerys circles looking for a way in.
• Fort Bokar and the western ramparts above the Pile inlet stand in for the Red Keep's seaward defences in the Blackwater material, including the rampart walks where Tyrion and Varys talk through the coming siege.
• The eastern walls near St John's Fortress and the old port supply the harbour views that establish the city from the water.

What the walls did not provide. Almost every King's Landing interior was a studio build in Belfast — the throne room, the Small Council chamber, the black cells and Cersei's apartments were sets at Titanic Studios, not rooms behind these parapets. The Blackwater battle itself was shot largely on sets, in a water tank and in effects, with the Dubrovnik ramparts supplying context rather than action. And the destruction of the capital in the final season was not filmed here at all: that sequence used a purpose-built street set in Northern Ireland together with locations in Spain. Guides who point at a specific arrow slit and name a specific death are usually improvising.

What you actually see today. Three entrances give onto the circuit: the main one just inside the Pile Gate beside the Franciscan friary, a second at Ploče near St John's Fortress, and a third by St Luke's Tower. Movement is one-way, anticlockwise, and the route is a continuous sequence of stair flights, narrow parapet walks and open terraces, with two or three tiny cafés cut into the wall on the sea side. The best-known detail is the roofscape: bright orange tiles mark buildings re-roofed after the shelling of 1991 and 1992, when the great majority of structures in the old town were hit, while duller, lichened tiles are pre-war survivors. From above, the damage map of the siege is still legible.

Getting round it. Allow ninety minutes to two hours for the two-kilometre lap, more with photography, and carry water. The stone radiates heat from mid-morning through late afternoon in summer, and there is no way to leave the circuit early once committed. Tickets are sold as a combined pass with Lovrijenac across the bay, valid the same day. Cruise arrivals concentrate between roughly ten and four; the first hour after opening and the last light of the evening are quieter and kinder to both the legs and the camera.