The Maiden Tower of Baku was built in the cylindrical form on the giant rock inclined towards the coast of the Caspian Sea. An oblong support (buttress) is attached to it from the seaside. The height of the tower on the northern part is 31 m, on the south- 28 m. The diameter of the tower on the first floor is 16.5 m. The thickness (width) of the wall on the first floor is up to 5 m. The interior part of the tower is divided into 8 floors. Each floor is covered with the arched ceiling made of cut stone. There are round holes in the middle of the stone ceilings. The holes are vertical. Thus when you look through the round holes in the middle of the 8 storey ceiling you can see the floor of the first storey. The single entrance to the tower is the arched doorway in its western part 2 m in height and 1.10 m in width.  The height of the first floor of the tower is 3 m, the average height of the other floors is 2.5 m.

The inter-floor communication is maintained by means of stairs built within the southern –east wall of the tower. It is interesting that the communication between the first and the second floors can only be maintained through the round hole in the ceiling by means of a ladder or a rope. It should be noted  that in past the door of the Tower was also multistage.

It is proved by the ruins of the structures remaining on the arched ceiling of the doorway which in length is equal to the width of the Tower wall (5 m). There were also several wells in front of the door in past. Thus, in the Middle Ages everybody who wished to enter the Maiden Tower had to carefully pass the wells, climb up the ladder to the door, pass through doors at the entrance and finally reach the first floor. A rope or a ladder was used to reach the higher floors through the central hole.

In order to keep under control the southern and southeastern sides, especially the sea, loopholes were made. They also served to ensure inward draft to the Tower. In 1962-63 archaeological excavations were carried out on the floor of the first stage of the Tower. The excavation conducted at the depth of 5 m revealed that the foundation of the Tower was built on the giant rock inclined towards the coast. Therefore a conclusion may be made that the buttress attached to the monument from the seaside acted as the principal support against the inclination.

During research works carried out in the Tower in 1964 it was found that there were big wooden beams 14 m in height stretched inward from the foundation. Their function is not known. Probably, these beams are related to a hidden construction inside the buttress or acted as amortization against the earthquake. This suggestion can only be clarified by means of electromagnetic waves given from both sides.

The thorough calculations have revealed that the thickness of the Tower wall at the base is 5 m while at the higher part it is 4.5 m. This shows that the base and the upper parts of the tower were built at the same time that disproves suggestions of some author regarding their construction in different periods. Because the wall 5 meters in thickness provided a strong foundation for the whole 12-meter Tower,  not only for its lower part. The secret of the preservation of the Maiden Tower is explained just with the fact that it is built on such a strong foundation.

One of the specific features of the construction design of the Baku Maiden Tower is a water well cut in the rock within the Tower. The well with a diameter of 0.7 m is within the southeastern wall of the Tower.  Excavation works were conducted in the well. The artifacts found in the well show that it has been used since XII AD. According to estimations, the well has no linkage with the sea water level. Chemical analysis of the well water showed that is good to drink. The well's mouth starts at the third floor level of the Tower descending along the wall at the depth of 13 m. To ensure safety the well is hidden within the Tower wall. Steps 10-12 m in depth are made in its northern and southern walls to move up and down. At the depth of 12 m, the wall becomes wider.

It is supposed that the secret underground passage between the Maiden Tower and the Shrivanshahs' Palace started just from the lower part of the well. The first underground passage revealed during the wide-ranging archaeological excavations carried out in the eastern part of the Icherisheher in 1982 is situated meridionally to the east of the street which goes beginning from the Shemakhy Fortress Gate towards the Salyan Gate and is considered to be the main commercial street of Baku.

It is worthy to note that the road line passes under the Multani caravanserai built in XIV AD and goes to the Maiden Tower. One of the reliable evidence for determination of the age of the Maiden Tower is a 0.4x0.6 m stone slab with an inscription placed at the height of 14 m above the Tower entrance on its outer side. The inscription says: "The Dome –Masud ibn Davud".  Some scholars suppose that Masud ibn Davud is the name of the architect who built the Tower. They rest this supposition on the inscription on a circular tower of the Mardakan fortress. The inscription on the Mardakan Tower says: "Architect Abd-Al-Majid ibn Masud ". The researchers believe the architect Abd-Al Majid was the son of the architect Masud who built the Maiden Tower. Also, it has been discovered that the inscription on the stone in the Maiden Tower was placed on the wall in a very careless way. It was negligently attached to the  section of the wall bound with stone framing. According to other researchers, the inscription was attached there when the Tower was built. As for the identity of Davud's son Masud, the medieval sources evidence that he was a grandson of the Seljuk Sultan Mahmud. Sultan Mahmud was a ruler of Azerbaijan at the beginning of XII AD. Perhaps in this period, his grandson Masud reigned over Northern Azerbaijan and this inscription was attached to the Tower wall at his desire to perpetuate his name.

The researchers, who on the basis of its structure, attribute the history of the monument to the ancient periods, state that it dates back to the Zoroastrian period – supposing it to be a Zoroaster cell, a fire-worshipper's temple or a building relating to goddesses Mithra and Anahita. To their opinion, the Maiden Tower which was the fire-worshippers' temple, can be built on the Caspian coast, among natural fires just in the ancient fire town "Fire Baquan"  in VIII- VII BCE under the influence of the towered temples of Caspiana and Midiya.

Based on the resemblance of the Maiden Tower to the Chiraq Qala defence Tower (donjon) many of scientists believe it is possible to say that it was part of the Gilgilchay defence system. Given resemblance of architectural elements of the Maiden Tower to the North-Eastern Albania donjons, it can be attributed to V-VI AD. As is known from the history,  Baku, which is considered to be one of the southern towns of the Caucasian Albania, was under influence of the Sasanian Iran. It is possible to suppose that the Maiden Tower was part of a defence system built in the southern periphery (occupied province) of the Sasanian Empire just in the territory of Albania.

The Maiden Tower which was damaged in various battles for ages was gradually rehabilitated and in the middle ages served the defence of the city together with the Baku Fortress wall. The changes to the construction of the monument also prove this. The Tower is of such shape that in case of a conquest of the city by an enemy, the ruler of the country and his entourage can close the doors and stand a long-term siege. As all these features are specific to all defensive Towers, therefore it could not be necessary to take such defensive measures for any temple, watchtower or observatory. Of course, it is not refuted that the tower was used purposively for its period. A resemblance of the Maiden Tower to the magnificent defensive Towers (Mardakan, Ramana, Shuvelan, Nardaran Towers) of Absheron can be noted.

A cavity in the form of a well accurately built with stone from the second floor to the seventh floor is within the south-western wall of the Tower. On each floor, there is a semicircular niche at the place of the cavity.  Within the cavity are pottery pipes 40-45 sm in length with the diameter of 25-30 sm and 2,2 cm thick walls which are set on each other downward. The joints of the pipes (surface and outer part of the wall) were mortared. Beginning from the first floor to the base of the Tower the pipes are replaced with quadrangular pottery gutters of 22x18 sm. The gutters go through the wall outward. Traces of a pottery wheel are clearly seen on the surface of the pottery pipes and gutters.

Archaeological excavations in the Icherisheher are going on. The artefacts revealed during the investigations are expected to contribute to the clarification of historical past   

of the Maiden Tower.