The medieval town of Ključ is mentioned in historical sources for the first time in the document of Sandalj Hranić Kosača dated 28.12.1410 (in castro Cluz) by which he authorized archdeacon Teodor to sign the agreement in Zadar on the cession of Ostrovica to the Venetians. It is located on the slopes of Baba mountain above Cernica (now the municipality of Gacko), this fortress town in the Middle Ages oversaw the most important Ragusan trade route in the territory under the rule of the Kosačas (Ragusa-Trebinje-Gacko-Čemerno-Foča), which makes it one of the most important towns of this region. Thanks to the Ragusa Road at the foot of Ključ, an open market developed in Cernica, where livestock, fabrics, wax and other goods were sold, while the guards in the Ključ fortress had the task of ensuring safe trade, in which they did not have any success, considering the frequent reports from Ragusa about robbing their merchants in this area. In addition to Ključ, Ragusan sources also mention Podključ (sotto Cluc), i.e. a sub-town which, unlike Cernica, had almost no economic significance in 1435.
According to popular tradition, which is nothing unusual when it comes to our area, the origin of the town of Ključ is attributed to the Ancient Greeks, while in historical studies it is usually assumed that it was built at the end of the 14th century by Duke Sandalj Hranić Kosača, for whom this town was one of his favorite residences. Sandalj’s close connection to the fortified town of Ključ is clearly visible from several Ragusan sources in the first half of the 15th century. A very interesting moment in Bosnian-Ragusan relations occurred in 1423, when it was recorded that Sandalj’s envoy did not have a valid deposit document with him when withdrawing money in Ragusa, it indicates that Ključ was the location of a part of the Treasury of this famous Bosnian magnate (Lett. di Lev., VIII, 140v, 04.01.1423). Furthermore, the sources mention a situation from 1426, when the Ragusans sent the nobleman Ivan Gundulić to Sandalj and his wife, in the direction of Ključ (via de Cluzi), with the aim of welcoming the married couple in connection with their planned visit to Ragusa, which happened at the beginning of the following year (Lett. Di Lev., IX, 95-95v, 10.01.1426). According to reliable information, Ragusa’s envoys stayed here on 1 January 1431 and wrote to their prince in Ragusa. Taking into account the fact that Ključ was one of the residences of the Bosnian Grand Duke Sandalj Hranić Kosača, we can assume, with the support of previous research, that court culture was developed there and that a luxurious court life was led, probably colored by the chivalric and courtly culture of the late Middle Ages.
The close ties of the noble Kosača lienage to the town of Ključ continued during the time of Sandalj’s successor, Duke and later Herzog Stjepan Vukčić Kosača. It was there, right after coming to power in 1435, that Duke Stjepan Vukčić conducted part of the negotiations with Ragusa, otherwise very arduous for both parties. Negotiations were being conducted in order to renew the contracts of his predecessor, (Cons. Reg. VI, 9′, 6. X 1435.). In Ključ, in April 1443, a certificate was issued to the Ragusans by which the duke confirmed that he had received an inheritance from Sandalj’s widow, and his aunt Jelena, the daughter of Prince Lazar, who was previously married to Đurađ II Balšić. The failed marriage negotiations of Herzog Stjepan Vukčić Kosača with Barbara of Lichtenstein were conducted in Ključ, where the herzog issued a document on 1 March 1455 that regulated his future wife’s rights. It is apparent from the above that this herzog’s town was of great importance to him over the course of his long-term rule, and therefore it remains unclear why Ključ is not mentioned in Alfonso V of Aragon’s charter from 1444, when he confirmed the possessions of his new vassal.
A few pieces of information about the town of Ključ have been preserved from the episode about the fall of the medieval Bosnian state. During the conflict between Herzog Stjepan Vukčić Kosača and his son Vladislav, which represents a sort of prelude to the downfall of herzog’s land, the Ragusans sent Bartol de Goze in 1462 with an order to reconcile father and son. On that occasion, Goze was suggested to look for the old herzog in Blagaj, Hum or Ključ. In the Ottoman attack in 1463, the town of Ključ was captured with considerable effort, but already on July 14 of the same year, news reached Ragusa about the return of this town to the hands of the Kosačas (Cons. Rog. XVII, 252′, 14. VII 1463). Ključ finally fell to the Ottomans in 1468 as a result of the merits of the general Ahmed.
The remains of the old town of Ključ are located on the slope of Baba mountain and are in a very bad condition. Throughout the 20th century, several researchers visited the ruins of the Ključ fortress, offering their analyses and observations about its construction. These observations suggest that the backbone of the town consists of three cliffs connected by walls on the east and west sides. The two parts of the town, upper and lower, are clearly visible, connected by a secret passage. The entrance to the town was found on the northeast side, where a chair is carved into the stone to the right of the entrance. In front of the town, near the mosque, there is another chair attributed to Duke Sandalj Hranić Kosača. For the mentioned mosque, folk tradition assumes that it was built on the spot where herzog’s church used to be, which is not necessarily wrong because it is known that the noble lineage of Kosača was active in building churches.
The nobleman Radonja Ratković died at the bottom of the town of Ključ, as it is engraved on his stećak that he died there under Ključ for his Lord, Duke Sandalj. Stećak was placed in the Military Museum on Kalemegdan in Belgrade in 1960. Thus, the town of Ključ remains the only medieval Bosnian town whose name is engraved on a stećak.
- Arheološki leksikon BiH, vol. 3, (ed. Borivoj Čović), Zemaljski muzej BiH, Sarajevo, 1988.
- Bešlagić, Šefik: Kamene stolice srednjovjekovne Bosne i Hercegovine, ANU BiH, Sarajevo, 1985.
- Ćirković, Sima M.: Herceg Stefan Vukčič-Kosača i njegovo doba, SANU, Beograd, 1964.
- Ćirković, Sima M.: Rabotnici, vojnici, duhovnici; društva srednjovekovnog Balkana, Equilibrium, Beograd, 1997.
- Dinić, Mihailo: Zemlje Hercega Svetog Save, SKA, Beograd, 1940.
- Dinić, Mihailo: Srpske zemlje u srednjem veku, Srpska književna zadruga, Beograd, 1978.
- Jorga N.: Notes et extraits pour servir a l’histoiredes croisades au XVe siecle, vol. II, Ernest Leroux, Paris, 1899.
- Kovačević Kojić, Desanka: Gradska naselja srednjovjekovne bosanske države, Veselin Masleša, Sarajevo, 1978.
- Kreševljaković, Hamdija – Kapidžić, Hamdija: “Stari hercegovački gradovi”, Naše starine, no. II, Sarajevo, 1954, 9-22.
- Kurtović, Esad: Veliki vojvoda bosanski Sandalj Hranič Kosača, Institut za istoriju, Sarajevo, 2009.
- Ljubić, Šime: Listine o odnošajih izmedju južnoga slavenstva i Mletačke republike, JAZU, Zagreb, 1878.
- Mićević-Đurić Tatjana – Soldo-Rešetar Valerija: “Likovne umjetnosti i obitelj Kosača”, Hercegovina, no. III, Mostar, 2017, 331-363.
- Pekić, Radmilo: “Cernica u doba Kosača”, Hercegovina, no. III, Mostar, 2017, 69-98.
- Šunjić, Marko: Bosna i Venecija (odnosi u XIV i XV st.), HKD Napredak, Sarajevo, 1996.
- Thallóczy, Ludwig von: Studien zur geschichte Bosniens und Serbiens in mittelalter, Duncker&Humblot, München-Leipzig, 1914.
- Vego, Marko: Naselja bosanske srednjovjekovne države, Svjetlost, Sarajevo, 1957.
- Vego, Marko: Zbornik srednjovjekovnih natpisa Bosne i Hercegovine, vol. 3, Zemaljski muzej BiH, Sarajevo, 1970.
- Zbornik Konstantina Jirečeka, vol. I, (ed. Mihailo Dinić), Srpska akademija nauka – Naučno delo, Beograd, 1959.