<P> The White Tower takes the form of a cylindrical drum 23 m (75 ft) in diameter with a height of 34 m (112 ft) above ground level, on top of which is a turret 12 m (39 ft) in diameter and 6 m (20 ft) high . Some of the embrasures in the outer wall of the tower are reached by a spiral ramp; others are accessed from a central room on each of the six floors . </P> <P> The turret houses a platform with a diameter of 10 m (33 ft), and the platform at the top of the main tower in front of the turret is about 5 m (16 ft) wide . </P> <P> The tower, which once guarded the eastern end of the city's sea walls, was for many years attributed to Venice, to which the Byzantines ceded Thessaloniki in 1423 . It is now known that the tower was constructed by the Ottomans sometime after the army of Sultan Murad II captured Thessaloniki in 1430 . Until 1912, an inscription in Ottoman Turkish verse above the door dated the structure to AH 942 (1535--1536). </P> <P> The historian Franz Babinger speculated that the work was designed by the great Ottoman architect Mimar Sinan, who is known to have built fortifications, including a similar tower at the Albanian port Valona in 1537 . </P>

When was the white tower of thessaloniki built