Project manager: Esther Ronen
Project engineer: Ing. Jacob Schaffer
Implementation of concrete vaults: Avner Gilad Building Conservation and Restoration Company, Ltd.
Planning architect: Arch. Ari Avrahami
Conservation planning: Eran Mordohovich
Conservation team leaders: Vadim Zeitlin, Johnny Peterson.
The Hall of Pillars is one of the largest and important structures in the Hospitaller Compound (the fortress). It was built in the twelfth and thirteenth centuries CE. The hall is characterized by a modular design; it measures 32.2 × 45.5 meters and consists of a set of twenty-four cross vaults resting on massive pillars. Each vault is c. 8 × 8 meters and c. 8 meters high. The original construction technology made it possible to create a very large, open and continuous space. The hall was built of dressed kurkar. The mortar used between the building stones and in the core of the pillars and walls was lime-based with aggregates consisting of ash, shells, limestone and kurkar. The vaults of the hall were treated with plaster whereas the walls were probably exposed.
The function of the hall in the Hospitaller Compound is still unclear. The hall might have been used as a dormitorium or as lodgings for the garrison stationed there.
Most of the hall had been exposed by the year 2000. The severe state of disintegration and the archaeological process of exposing the remains previously necessitated massive engineering and conservation intervention designed to prevent the collapse of parts of the structure that were still standing, and particularly the collapse of the Ottoman buildings that had been erected above the Crusader hall and which currently house the Museum of Underground Prisoners.
Due to its complexity, the hall became the scene of experimentation over the years for different types of conservation approaches, methods and processes. These measures left their mark on the hall’s appearance and could no longer be identified as a uniform architectural complex.
About two years ago another tourism development project was begun in the Hospitaller Compound. Its goal was to turn the site into an experiential visitor’s center focusing on ʽAkko in the Crusader period. Within the framework of that project engineering and conservation steps were defined that were meant to remove hazards, prepare the necessary infrastructure systems and implement the conservation measures in those areas where the tourism experience would take place.
The main conservation measures that were defined for the Hall of Pillars included:
1. Reinforcing the field of pillars.
2. Restoring the vaults in the southern part of the hall.
3. Completing the restoration of the hall’s western facade.
4. Conserving the remains from the Hellenistic period which predate the construction of the Hospitaller hall.
The Field of Pillars
The original pillar structure consists of the pillar’s base, the trunk of the pillar (1.80 × 1.80 m), the cornice strip that protrudes from the plane of the pillar (on which the arch of the cross-vault is supported) and the heel of the vault, which is composed of three rows of stone at the base of the vault’s radius.
Many of the pillars that survived were encased in a concrete and steel form so as to prevent their collapse. Rows of stone in some of the pillars remained exposed and some of these stones were cracked or disintegrating. The process was further exacerbated by the exposure of the hall and it reached the point where the stability of the pillars and the original stone vaults above them were at risk.
In order to maintain as much of the original stone construction as possible it was decided to replace only the corner stones and those that were worn down to a great depth.
First all of the exposed rows of stone were documented and each stone was analyzed from the standpoint of its size, shape and location in accordance with the plane of the original pillar. The new stones were hewn and inserted into position on the basis of this analysis. On one of the pillars it was also necessary to replace the entire row of stones in the cornice, which necessitated manually dressing the profile that characterizes the different stone elements in it.
Restoring the Vaults
Before the start of the current project the vaulted ceilings of the hall had three different appearances, as a result of destruction that occurred in different periods. Original stone vaults were preserved in the middle of the hall. In the northern part of the hall a vault had collapsed during the excavation in the 1990s. The solution that was implemented at the time was to cast concrete vaults which were later painted.
The vaults were not preserved in the southern part of the hall. Concrete pillars were cast there as well as part of a flat concrete ceiling. The goal of the intervention was to restore the static schema to the structure and thus prevent further destructive processes.
In the current intervention we were required to define the hall’s space more clearly and to tone down the different appearances that had been created as a result of the engineering and conservation intervention that were correct at the time they were implemented but did not give the hall an optimal appearance.
With this in mind it was decided to restore the volume of the missing vaults and to remove two and a half vaults in the southeastern corner that had been left open for the purpose of maintaining traces of the hall’s structural, conservation and engineering history. After numerous discussions it was decided that the vaults would be built of concrete following their original geometric outline. In order to provide constructive support for the modern vaults two of the pillars of the southern wall were restored in stone to the height of the heel of the vault. Casting the vaults was a conservation and engineering challenge owing to the irregular geometry, the connections between the original and new elements and the need to create support for the new vaults on the existing building’s components. By the end of the process we had succeeded in achieving our primary goal and today there is uniformity between the regions where the vaults were restored and the original geometry of the hall is considerably clearer.
Completing the Restoration of the Hall’s Western Facade
The courtyard and the western façade of the hall can be seen in Cornelius de Bruin’s famous drawing of 1679. The building in the drawing was identified when the façade was exposed in excavations conducted in the 1990s. After having completely exposed the hall and the courtyard, the destroyed arch was restored. Below it stood the remains of the Crusader nonbearing wall, c. nine courses of a wall consisting of two sides and a core of mortar and rubble.
The completion of the nonbearing wall and the window in it was meant to tone down the stylized “dissonance” that characterized the atmosphere in the hall, as well as improve the lighting and climatic conditions within it.
As a first step the special and intricate geometry of the window was studied, as were the angles of its different sills and the original manner in which it was assembled. The latter was based on identical windows that survived in this facade (some of which were previously conserved and restored).
In the second stage the matter of supporting the new stones on the existing wall was considered and it was decided to replace some of the original stones so as to ensure sufficient support for the new nonbearing wall and the window’s stones.
Next, the unique geometry of each stone and its angles were depicted by means of a three dimensional digital model. This was done to more than seventy stones in all. Accordingly, the stones that the supplier brought to the site were cut so precisely that all the conservation team had to do was a minimal fitting of them when the wall was being built. The construction included replacing worn stones below the window sill, building the nonbearing wall, filling the core of the wall and in the end mounting the upper lintel that was more than 1.50 meter long.
Upon completion of the construction and the installation of the lattice the hall was illuminated as it was carefully designed to be 800 years ago.
Conserving the Hellenistic Period Remains
In 2006, ancient architectural remains predating the Crusader period were discovered during an excavation in the floor of the hall while preparing the infrastructure of an underground space. These were dated to the Hellenistic period (second century BCE). The importance of these remains lies in the fact that they constitute evidence of the earliest settlement on the ʽAkko peninsula, they are representative of typical Phoenician building technology and they are the beginning of a construction sequence that had started in that period and has continued until the present.
Among the interesting Hellenistic artifacts: a nonbearing wall made of stone dressing debris with a catapult stone incorporated in it, doorjambs and foundation walls of buildings. The wall remains, founded on the bedrock and built in the form of boxes consisting of ashlar stones with fieldstone fill between them is characteristic of the Phoenician building technique.
The conservation measures included stabilizing the earthen sections created in the excavation, as well as stabilizing the Phoenician walls and the bases of the Crusader pillars that penetrated the earlier strata down to the level of the bedrock.
An elliptical path and a railing were built around the excavation pit where the Hellenistic finds are displayed, thereby allowing the public a glimpse of this phase of ʽAkko’s past.
