The clock tower, at 30 metres, is the tallest in all of Bosnia, and dates back to the 17th century when it was constructed by Gazi Husrev-beg next to the mosque that also bears his name. The tower has a staircase with 76 wooden steps arranged in a square, and displays the time on all 4 sides. When Eugene Savoy of the Austrian army laid siege on the city in 1697 and looted it, the tower was set on fire, but restored in 1762. After the Austro-Hungarian occupation, the upper part of the tower was upgraded, and the decaying Turkish clock mechanism was replaced by a new one from Gillet & Johnston, made in London in 1873. The original clock mechanism was moved to the Vratnik mosque where it remains on display until today. The last upgrade dates from 1967, when the dials were gold-plated. A peculiarity of the clock tower is that it appears to be the only remaining clock tower in the world that displays the lunar clock (a la turca, lunar reckoning). This method of measuring time counts hours up till the moment of (astronomical) sunset instead of midnight, as with contemporary time calculation, so the hands are in the 12 o'clock position at every sunset, when a new day also begins. Since the setting of the sun is uneven throughout the year, the time needs to be manually controlled and recalibrated every 2 to 3 days. The task of recalibrating the clock was assigned to the muvekit (timekeeper), who used astronomical instruments in a special room called the muvekithana to calculate the position of the sun. The current muvekit, Mensur Zlatar, who works at a nearby jewellery shop, has been assigned the responsibility since 1960s. The exact timing of the sunset used to be an important moment for locals to schedule their time of prayer, but the original religious purpose behind the lunar time has long since had its meaning forgotten, causing many to think that the clock is simply bad at proper time keeping. In 2006, the Commission for the Preservation of National Monuments proclaimed the clock tower as a national monument of Bosnia and Herzegovina. The tower cannot be visited, but it is possible to stand at its base by following the tunnel leading to Pekara Imaret right next to the tower.