used in the medieval city surrounding it. This conclusion is partly supported by historian Prof Bretanitskiy who has postulated that the tower was partly built in the 5th to 6th centuries and then later in the 12th century. The site was believed to have been used originally during the Sasanid era as a Zoroastrian temple. An inscription located 14 metres high on the south wall which in old Kufic script mentions Qubbeye Masud ibn Davud or Kubey Mesud ibn Da’ud, an architect active during the 12th century; he is the father of the architect who built the Mardakan Round Tower. However it is disputed as the inscription, unlike the Mardakan Tower inscription, does not actually reveal him to have been the architect, although it is generally agreed that much of the modern tower dates back to the 12th century. Prof. Ahmadov believes that the tower was used as an astronomical observatory from the time of this reconstruction, due to the fact that 30 hewed stone protuberances on the tower's lower section and the 31 protuberances on the upper section, linked with a stone belt, correlate to the days of the month. According to recent archaeological excavations, carried out in 1962–63 on the ground floor of the tunnel, the tower was built on a large rock sloping toward the sea, and the buttress structure projecting out from the main tower provided stability to the tower. Further excavations have also revealed wooden girders, each high, at the foundation of the tower. This has been inferred as an earthquake-resistant design. It has also been conjectured that the cylindrical shape of the tower with thick base walls tapering to ( is also mentioned) provided the solid foundation on which it has survived over the centuries. It is also mentioned that the tower was built at one go and not at different times as inferred by other scholars. The tower and other wall structures now under the UNESCO list were strengthened during the Russian rule in 1806 and have survived. The Maiden Tower is depicted on the obverse of the Azerbaijani 1 to 250 manat banknotes of 1992–2006, and of the 10 manat banknote issued since 2006, as well as on the obverse of the Azerbaijani 50 qəpik coin minted between 1992 and 2006 and the reverse 5 qəpik coin minted since 2006. Legends and mysteries There are various mysteries and legends related to Baku