the distance as a man-made structure. The defensive capabilities of the fortress have been tested through history in many military operations. During the centuries of its use, the structure served various armies and has undergone a number of renovations, to keep up with the development of arms. The original appearance of the fortress is no longer known, due to the structural changes undertaken by Croatian nobility, Turks, Venetians and Austrians. The present day aspect of a mostly stone fortress dates back to the restructuring work carried out by the Venetians in the 17th century. First defensive line Many buildings of the Klis Fortress which are from 17th through 19th centuries are partially or entirely preserved. The Fortress actually consists of three parts, enclosed by walls with separate entrances. The first main entrance was built by the Austrians in the early 19th century, on the place of an earlier Venetian entrance. Left of the entrance there is a fortification erected by the Venetians in the early 18th century. Also, near the main entrance there is a "position Avanzato" built in 1648, which was repeatedly renewed afterwards. On the ground floor of the fortification there is a narrow over-vaulted corridor, which is called a Casemate. Second defensive line The second entrance which was significantly damaged in the siege of 1648, leads to the former medieval part of the fortress previously ruled by a Croatian nobility. After 1648, Venetians fully restored the second entrance, but its present appearance was made by the Austrians during the early 19th century. Along the northern wall near the second entrance, there is fortress-tower called "Oprah", the most important medieval fortification of the western part of the fortress. It was mentioned for the first time in 1355, but later the Venetians made the lower crown on it. Nearby of the entrance are artillery barracks, built by the Austrians in the first half of the 19th century. In 1931 its upper floor was ruined, so now only the ground floor remains. Third defensive line The third entrance leads to the former medieval part built in the early Middle Ages. The Venetians renewed it several times after conquest in 1648, and the last upgrade was in 1763. Within this part of the fortress there is the side tower, built during the 18th century, and completed in 1763. Following is a repository of weapons built in the mid-17th century and old