First defensive fortifications
First defensive fortifications are located on far west of the Fortress. Interior of the Fortress is accessed through first entrance near which, somewhat northward, there were the first gate in the Middle Ages. That gate, along with nearby fortifications, were partially demolished by Venetians during siege in 1648.
This semi-circular gateway was bulit during Austrian reign in the 1820s, after the old simple Venetian gateway (Porta del Primo Recinto) was removed from this place. Its terrace on the top is enclosed by a low wall.
Earlier, the gate had double doors, and that is detectable through preserved grooves on its walls that were intended for wooden doors.
Even earlier the gate, according to preserved remains, were also two-sided and wooden. They were reinforced with large wedges on the outside, and they were secured with locks, latches and joists on the inside. Interspace could be filled with earth at time of siege, which would then contribute to gate firmness in case of cannon fire.
Entry fortification and position Avanzato
Position Avanzato was mentioned for the first time as front position (Posto Avanzato) in 1648. Its purpose was to protect the first and the second gate which, because of its position and then increasing use of siege artillery, presented weak point of the Fortress defense. Venetians have rebuilt it several times until mid-18th century. Then, on the north side, they raised a high protruding prow. It was also called position Tenaglie (eng. pliers) because of its L-shape.
Second defensive fortifications
Second defensive fortifications extend to the central part of the Fortress, between the first and third gate. It is separated by wall sections and forts.
This fortified entrance (Porta del Secondo Recinto) with a terrace on top is approached from west by steep slope that was tiled in the 1930s. There already existed a medieval entrance there and it was heavily damaged in the siege of 1648, but Venetians subsequently renewed it completely.
Bulwark towards Megdan
Oprah Tower and remote east position called Scala are connected by a long bulwark towards Megdan (Cortina verso il Meidian) with series of loopholes. From southern side of the bulwark, there is a narrow guard trail that also served as a defensive position. By the middle of the 17th century, the bulwark had a late-medieval appearance with a characteristic toothed top whose height was somewhat lower than it is now.
This medieval tower was once the most important defense stronghold of western part of the Fortress. It is mentioned for the first time in the report of Pavao III Šubić in 1355 by name Oprack, while in Ottoman times it was named Pasha Tower. In the mid-17th century, Venetians named it Torretta (eng. turret, tower), and that name was later used by Austrians as well. However, the tower retained its original Croatian name Oprah throughout time and it is still called Oprah today.
Located western of bastion Bembo, position Scala occupies a smaller space of an irregular square shape. It is enclosed by relatively thin walls where four loopholes existed earlier, and today there are two broad openings for cannons.
In the twenties of the 19th century, Austrians made a curved earthen ramp and an artillery barracks building. In 1931, its upper floor was demolished, while the ground floor remains still preserved today.
Sidelong fortifications of irregular rectangular shapes extended below the artillery barracks. The largest elongated fortification was called position Mezzo (eng. middle). In the time of Venetian authority there were guardhouse, two smaller houses and fortified entrance that was used for communication with eastern and southern parts of the Fortress until the beginning of the 18th century.
Water supply was an important factor in defense of Klis, who was often exposed to long lasting sieges, and in such circumstances its defenders lacked water. Since there were no natural springs in the Fortress and no possibility of building wells, only solution to this problem was construction of water cisterns. They were built in places where was usually the greatest need for water in time of a siege.
Southern part of the fortifications
At eastern end of bulwark above Varoš, there are two smaller walled up openings of former side entrances through which one could exit and enter the Fortress unnoticed.
Third defensive fortifications
At elevated part of cliff, strategically well suited for defense, there are third defensive fortifications, which were also the Fortress' most significant part. Raised above the other fortifications, it represented a dominant and a center of the Fortress and also final defensive line of Klis. At the times, at this position, there was an Illyrian fort and then Roman "castrum", on which foundations one of the first old Croatian fortresses, the seat of medieval Croatian kings, was built.
Third gate are approached by a wide tiled stairs leading to entrance that was made as a passage through guardhouse. In front of the gate there is a smaller defensive area (Barriera) on whose walls are narrow loopholes. South-east corner of the gate is supported by high lateral tower (Torre Bastionata) of irregular rectangular shape, whose walls of different stone structures point out several stages of its construction. Established in mid-18th century, and according to historical data completed in 1763, the tower was intended to defend the gate and part of settlement Varoš.
In mid-18th century this area was armory position (Piazzetta della Monizion), while western part of its southern wall was called Corner (Mura Corner). One of the oldest water cisterns is located behind entrance along steps. It has an irregular rectangular shape with a semicircular arch, above which is an enclosed terrace. Opposite of the cistern there is a ruin of ammunition and weapons storage (Munizioni) that was later used by Venetians as storage of tools, and at the time of Austrian authority it was storage of cannon stands.
Small quarters are reached rising from armory position by elevated stairs to upper, more spacious area that had a simple arch entrance. Initially, that was an armourer's apartment, and later it was intended for an accommodation of officers and soldiers.
Duke's quarters / governor's residence
Duke's quarters (Knesi Cucha) or governor's residence (Alloggio del Proveditor) or palace (Palazzo del Proveditor) extends on rocky cliff north of the mentioned stairs and the armory position. It may have been built on foundations of the oldest buildings from the period of medieval Croatian kings and dukes. According to Venetian sources, at the entrance there was a governor's office (Officio provisorio) or a chancellery (Cancelleria), on the ground floor there were storages and rooms for officers, guards and servants. On the first floor, which had two smaller northern entrances, there were officers' rooms, reception, living room, service room, kitchen and pantry. At the beginning of French government, judge and his secretary were stationed in governor's residence for a short while, but they had to leave it for its friability. After Austrians restored it in the 19th century, commanders of the Fortress and military engineers were accommodated there.
Bastions Bembo and Malipiero
At westernmost part of this defensive area, at the place where Kružić's tower was once, today is bastion Bembo, the largest artillery position in the Fortress. Towards the east, it is connected by bulwark behind the church to central pentagonal bastion Malipiero. Bastion Malipiero is enclosed by high walls in which there were broad openings for cannons, and now those are narrow. Below it, there is vaulted passage that stretches to the eastern position Maggiore.
This second-largest location in the Fortress is also protected by high walls with funnel openings for cannons. In its north-west corner there is a large gunpowder storage built by Austrians in the 1820s.
The most protruding part of this defensive fortifications, and therefore of the Fortress itself, takes up narrow raised prow of position Šperun (Sperone, Spiron). Hill Ozrna and road passing from the east were once overseen from there. Until Venetian conquest of the Fortress, there was high Duke's tower that was severely damaged during the siege. From former high walls of this position, especially of north wall, only low parapets with a series of loopholes have been preserved till today.
Church of Saint Vitus
Church of Saint Vitus is situated between bastion Bembo and bastion Malipiero. The church stands out as the most beautiful building in the Fortress. Almost entirely preserved, this former Turkish mosque, built on foundations of medieval church, is one of rare examples of Islamic architecture on Dalmatian soil. It was built immediately after the fall of Klis in 1537, and served to Turks for performing religious ceremonies. When Venetians occupied the Fortress in 1648, the mosque was converted into Church of St. Vitus. The following day sacred Mass was served there and it was attended by General Leonardo Foscolo. Venetians have knocked down minaret and built quarters for officers in its place, which were there until the early 19th century when they were removed.
In western wall, there is a shallow rectangular niche with a built-in washbasin with stone frame, decorated with shallow relief with motifs of trophy weapons and with other decorative elements. This Baroque washbasin dates back to the 17th century. It is believed that it once stood in the governor's residence from which it was transferred to the church, where a large stone shell was added to it as a holy water stoup. On low octagonal column, right of the entrance, a smaller holy water stoup was constructed with engraved year of 1658, which certainly marks time of its placement. There is an inscription in Latin engraved in a stone placed above the entrance and in translation means:
what faith has built
faith will preserve
There were three altars in the church: the main altar dedicated to the Fortress patron St. Vitus, altar of Blessed Virgin Mary and altar of St. Barbara. From once rich church inventory, nothing has been preserved in the Church of St. Vitus.