Since the lighthouse of Alexandria is demolished we can estimate its height only through the documents that were written by the witnesses of the time as well as by representations that we would judge reliable. Unfortunately for the latter, we can not use them to know the dimensions of the monument because on the one hand they lack precision, on the other hand they were made at a time when the artists could not yet reproduce what " they saw precisely, as it could have been done during the rebirth. Moreover, each artist had his own interests in the representation of the lighthouse, some wanting to show it bigger than it is, for example to make more insignificant boats that would have been at his feet, others would have reproduced it more massive, to give it a menacing appearance, etc. So we can only rely very little on these representations, even though, in most cases, they allow us to see the general form that he had: A monolithic block with a square plan at the bottom, a second stage of an octagonal plane and a third one cylindrical, each stage having an internal staircase (or a ramp, for the first stage). To know the dimensions of this monument today is therefore not easy.
The height of the lighthouse
However, to know the height of the lighthouse of Alexandria, one must rely on the documents of the time. The most interesting is of Al-Andalusi, it was written in 1117, shortly before its serious demolition in 1303. Here is what it describes it:
The entrance to the Lighthouse is very high. It is accessed by a long 183-meter ramp. This is based on a series of arches [...]. Once we reached the top of the first floor, we measured its height above the ground with a piece of rope to which we attached a stone. We found 57.73 meters [...]. In the center of the terrace of this first floor, the building was prolonged, but with an octagonal shape [...]. This second floor was higher than the first. [...] We debouched in the center of the second terrace [...]. The building was still prolonged in a cylindrical form [...]. We measured the height with our rope: 7.32 meters. On the terrace of this third floor, there was a mosque with four doors and a dome.
According to Al-Andalusi, the heights were thus:
Height of the 1st floor: 57,73m
Height of the 2nd floor: Supérieur à 57,73m
Height of the 3rd floor: 7,32m
By cross-checking other sources of information the heights become clearer and we can obtain reliable figures, and we find that they differ from those of Al-Andalusi, especially for the height of the second part, much smaller. The total height of the building was 135m, cut in 71m for the first floor, 34m for the second and 9m for the third. The floors had a square plan, the first one was 30m wide, the second a little less than 20m and the third was relatively narrow, but we do not know the width.
The commonly accepted heights are therefore rather the following:
Base height: 21 m
Height of the 1st floor: 71 m
Height of the 2nd floor: 34 m
Height of the 3rd floor: 9 m
Total height: 135m
Are these numbers reliable?
No, clearly not!
Today, exact figures can not yet be known, but underwater excavations are underway and, twice a year, improve knowledge of the subject. Perhaps in a few years we can know exactly all the coasts of this magnificent monument, but for now we have only estimates. Moreover, according to the documents, the height varies from 110 to 135m, nobody can not clearly affirm. However, we note that there are no significant variations, we are in estimates of plus or minus 15%, it seems to indicate that these figures are not so false. They are just to refine.