EL-NABIH CISTERN: the historical and architectural study, and the initial excavations

The archaeological excavation
 
Laurent Borel & Chrystelle March, architects
with Samuel Desoutter, archaeologist
February 2007

The known and the unknown

The first unknown concerned the way the cistern was built. We were looking to understand whether the walls of an already existing cavity had been stabilised or if a hole had been dug into which the reservoir was installed. At the same time, we wondered if the walls of this cavity reached up to the height of the cistern’s cover. We also hoped to find out how the transition between the two forms of roofing was created. A further question concerned how the cistern functioned.
We were particularly hoping to identify the function of the conduits visible on the inside southern wall of the reservoir. We also wished to confirm whether the upper part of the cistern stood above ground level, as we had supposed, and we were keen to discover the remains of the “magasin des artilleries” so that we might understand its architecture and its relation to the cistern.
The third great unknown concerned the dates of construction and restoration, and the installation of the military storehouse. Until now, there is only the capital dating to the second half of the 6th century AD that gives us a terminus post quem for the construction of the cistern. And while the documentation of the “Kamil Files” shows us that the restoration work was before 1896, we would like to date it with precision. Finally, the “magasin des artilleries” only appears on maps after the second half of the 19th century and so we presume that its construction is from this period (fig. 12).
Fig. 12 : General view of the cistern showing its situation within the urban context of the town and the two exploratory trenches of the excavation. Photo : L. Borel © CEAlex.

Explorations
Fig. 13 : General view of the cistern showing the two exploratory trenches of the excavation. Photo : L. Borel © CEAlex.
The first excavation campaign, of summer 2006, is now delivering initial results. Two large exploratory trenches were dug running north-south and east-west, and centred on the principal opening for drawing water (fig. 13).

The northern exploratory dig uncovered the summit of the cistern at less than 0.13m down, beneath a layer of rubble. The extrados (curved exterior) of the groin vaults is covered with a pavement that slopes at about 6% in towards the central well. The north wall, slightly thicker than the others, rises to the height of the roofing system. Some 0.75m to the north, the southern wall of the “magasin des artilleries” was discovered lying 0.8m beneath the surface (fig. 14). The southern end of this trench exposed the barrel vaulting at less than 0.05m down. The flanks were full of rubble and the extrados clear of any pavement. The vaults seem to rest upon the original walls that have been partially dismantled. A masonry channel, running from the south-east, pierces the stonework of the diaphragm wall and opens into the second span to the west (fig. 15). The exploration to the west uncovered the barrel vaults less than 0.05m down. Their flanks were also filled and the extrados clear of any pavement. The top of the western wall of the reservoir reached the first third of the vaults whose lateral thrust it bears. The lower part of this wall that could correspond to the first stage of building has not yet been revealed in this zone. About 1m further west, an area of slabs has been uncovered at less than 0.15m down. It covers a very compact layer at 0.25m deep. Lastly, the eastern trench exposed the top of the second barrel vault at less than 0.05m beneath the surface. The extrados of the adjacent groin vault has been cleared of its pavement. At the junction between these two covering systems, a wall seems to bear the lateral thrust of the barrel vault.

Fig. 14 : View of the pavement and the wall of the “magasin des artilleries” in the northern trench (looking from the north). Photo : L. Borel © CEAlex.
Fig. 15 : View of the southern edge of the barrel vaults and the channelling in the southern trench (seen from the south-east).
Photo L. Borel © CEAlex.

Initial interpretations

Thus the excavation demonstrates the construction methods of the cistern. We can see that the walls of the reservoir reach to the pavement that covers the groin vaults. To the south, the walls were cut back to allow the creation of the barrel vaults. To the east and west they were extended to a third of the vault to compensate for the lateral thrust. The difference in height of the two systems is shown structurally and was, it would seem, simply hidden by fill (Fig. 16).

The discovery of the pavement sloping towards the central well tells us about how the cistern originally functioned. We should, of course, verify the extent of this layout, however, we can already suppose that this pavement formed a sort of impluvium that allowed for the collection of rainwater as a complement to the annual filling of the cistern from the underground network.

The conduit discovered corresponds to a square opening, visible inside the reservoir, above circular piping some 0.20m in diameter. These elements are part of the water supply and overflow system of the cistern from after the reshaping and lifting of the southern part of the roof, since they are positioned above the level of the groin vaults.

We can thus presume that the equivalent conduits, corresponding to the first form of roofing, are those situated in the central span at a slightly lower height. The ground level discovered to the west might present a weak clue as to the emergence of the cistern from the ground in its original form .It could be connected to the role of the “magasin des artilleries” and have served as an access ramp from the street. Since the excavation was limited to a depth of 1.5m for obvious reasons of safety, we were unable to reach the foundation levels. Nevertheless, the layers explored were rich in archaeological material and the study of such should provide elements for dating (Fig. 17).
Fig. 16 : View of the wall bearing the thrust of the barrel vault in the eastern trench (seen from the east).
Photo : L. Borel © CEAlex
Fig. 17 :View of the wall bearing the thrust of the barrel vault in the western trench (seen from the west).
Photo : L. Borel © CEAlex.
If you entered the site by this page, click here to open the menu window