The oldest single arch stone bridge in Mostar, the Kriva Cuprija ("Sloping Bridge"), was built in 1558 by the Ottoman architect Cejvan Kethoda. It is said that this was to be a test before the major construction of the Stari Most began. The Old Bridge was completed in 1566 and was hailed as one of the greatest architectural achievement in the Ottoman controlled Balkans. This single-arch stone bridge is an exact replica of the original bridge that stood for over 400 years and that was designed by Hajrudin, a student of the great Ottoman architect Sinan. It spans of the Neretva river, above the summer water level. The Halebija and Tara towers have always housed the guardians of the bridge and during Ottoman times were also used as storehouses for ammunition. The arch is a perfect semicircle in width and in height. The frontage and vault are made of regular stone cubes incorporated into the horizontal layers all along the vault. The space between vault, frontal walls and footpath is filled with cracked stone. The bridge footpath and the approaching roads are paved with cobblestones, as is the case with the main roads in the town. Stone steps enable people to ascend to the bridge either side. During the armed conflict between Bosniaks and Bosnian Croats in the Bosnian War in the 1990s, the bridge was destroyed by the HVO (Croatian Defence Council).