Differential earthquake footprints on the masonry styles at Qal’at al-Subayba (Nimrod fortress) support the theory of its ancient origin

Qal’at al-Subayba, one of the largest medieval fortresses in the Middle East, is located on the foothills of Mount Hermon, four kilometers east of Banias, 33° 15′ 10″ N, 35° 42′ 53″ E on the DNS. The fortress is situated on a narrow ridge, 120 m wide and 430 m long, about 800 meters above sea level, and is naturally protected by steep slopes on its southern, western, and eastern faces, and by a deep ravine to the north. It is strategically located on the ancient road from Tyre to Damascus [1–3]. It dominates the ancient city of Banias (formerly Paneas or Caesarea Philippi) and oversees a vast area, from the Hula marshes to the Ayun Valley (Fig. 1). The only road to the fortress comes from the east and passes below its eastern curtain wall. Its donjon is situated on the highest point of the ridge facing east. The donjon is protected by inner curtain walls and a moat to the west. A schematic description of the fortress compounds and layout is provided in Fig. 2. Although the fortress bears distinct earthquake footprints, many of its sections remain, providing a very fine example of medieval fortress design. Different masonry styles were used in construction. This feature is unique and is not found in other medieval fortresses in the region. Nimrod fortress was declared a National Park in 2003 and is considered an international heritage site and a major tourist attraction.

The first European explorer to visit the site was Ulrich Jasper Seetzen in January 1806. Later, it was visited by numerous explorers, among them John Lewis Burckhardt, Lawrence Oliphant, and Edwin Hodder. The famous nineteenth century explorers, Edward Robinson and Sir Charles William Wilson, who each visited the site in the mid-19th century, described Qal’at al-Subayba as a strong fortress built using different masonry styles from ancient to medieval times [2, 4]. Paul Deschamps explored the fortress in the early 1930s. Deschamps did not subscribe to the ancient origin of the fortress; he argued that the entire fortress is Medieval with typical Templar characteristics [5]. Ronnie Ellenblum, in his manuscript “Who Built Qal’at al-Subayba?” proposed that the fortress was established in the post-Crusader era between A.D 1220 and 1230 by the Ayyubic ruler of Banias, Al-Malik Al-Aziz ‘Uthman [3]. The Ayyubic theory gained wide popularity and is currently accepted by most scholars [6–9]. However, it is based on an interpretation of historical texts, rather than on firsthand observations or archaeological findings [7]. In addition, the theory does not explain why and how a local ruler constructed such an impressive fortress in a time of war, far from the front, when the necessary resources and professional human workforce were scarce.

A current day visitor to Qal’at al-Subayba cannot ignore the wealth of different masonry styles at the site. Each style has its unique characteristics, from stone size and stone dressing to architectural design. Some of the styles are stratified, one upon the other. As masonry and architecture styles are oftentimes linked to a specific historical era and/or ruler [10], these observations suggest that construction was carried out by different masons during different historical times and under different rulers.

The fortress compound bears clear and distinctive earthquake footprints [9]. These footprints were attributed to a single earthquake, that of A.D 1762 [3, 6]. However, close examination of the earthquake marks on the different masonry styles reveals that they were affected differently. While some constructions were severely damaged or even collapsed, others were damaged to a lesser extent, sustaining partial collapse and cracks. Yet others were unaffected and have no visible earthquake marks. These observations lead to the hypothesis that the fortress was constructed over a long period and struck by at least two different earthquakes. According to this hypothesis, the fortress chronology can be divided into three periods, early (before the first earthquake), middle (between the first and the second), and late (after the second earthquake). Associating the different masonry styles to these chronological periods and identifying the relevant earthquakes based on the historical earthquake record might provide a better understanding of the fortress history and when it was founded.

Although the wealth of masonry styles is a recognized feature of Qal’at al-Subayba [2], scholars have generally overlooked its significance. This study focused on the different styles, characterizing each according to stone size, stone dressing, architecture, and similarity to masonries in other fortresses. Using these criteria, it was possible to identify four primary styles, Massive, Crusader, Ayyubic, and Mamluk. The description of each style together with its earthquake footprint is provided below.

The Massive masonry is restricted to the Northwestern Tower and adjacent stone wreckage (see Fig. 2 for location). This masonry is characterized by rusticated, trapezoid ashlar of 2–5 m width, 1–2 m height, 1–2 m depth block, weighing between five and 30 tons each [6]. The outer face of the stones’ surface is rough, but their contours are delicately and accurately cut and each stone was carved individually to fit snuggly to its neighbors (Fig. 3a, b). The black line under one of the stones in Fig. 2a measures 5 m length. The quality and precision of the stone dressing are outstanding and, despite their size, each stone was individually fashioned for distinctive shape and role [6].

Notwithstanding its immense size and durability, the Massive masonry sustained earthquake damage on a catastrophic scale, as most of the tower’s western face, as well as internal sections utterly, collapsed [9]. The northern (Fig. 3c) and the southern (Fig. 3d) faces were better preserved, indicating that the horizontal earth motion was south-west. Of the inner sections, a long and narrow corridor termed the ‘secret passage’ was virtually preserved (Fig. 3e). Interestingly, the two battlements along this corridor are not of the medieval type with narrow arrow slits for crossbow archers, but rather large arrow slits designed to accommodate arrow ballistas (polivolos katapeltes) of the type common in antiquity (Fig. 3f).

The huge wreckage piles to the west are the best evidence of the earthquake’s destructive force. The scattering of the stones reaches a radius of about 30 m and the piles cover a very large area on the western slope (Fig. 3h). Although many of the stones were removed during modern reconstruction activity, the scattering provides quite a good impression of the radius and size of the wreckage. Smaller wreckage piles are located to the east and the north; however, many of the stones were removed or replaced. Sections from a monolithic spiral staircase found among the western wreckage (Fig. 2g) suggest that this section served as a watchtower. The black line in the middle of the image measures 1 m length.

The Massive masonry encircles an inner tower built in a different masonry style, namely Crusader masonry. Hartal maintained that the Massive masonry was a later addition by the Mamluk ruler Badr ad-Din Bilik, [6]. The current observations do not support this view and suggest that the Massive masonry preceded the other masonry styles at the northwestern tower. This conclusion is based on the following: (1) the Massive masonry sustained the lion’s share of the damage while other masonries in the same location were only moderately affected; (2) the wreckage piles comprise only Massive building blocks which would not be possible if both Massive and Crusader masonry constructions existed at the site when the earthquake hit; (3) this type of masonry requires special skills, know-how, resources, time and a huge working force. It is unlikely that these were available to a local ruler.

Crusader masonry is the predominant masonry of the fortress and can be identified throughout the compound. This masonry is characterized by medium-sized, rusticated rectangular blocks (roughly 100 × 75 × 75 cm). The central portions of the blocks are roughly dressed and surrounded by flat rims (Fig. 4a). The stone dressing displays precise and fine workmanship and the stones fit snuggly together. The black line that crosses one of the stones in Fig. 4a, measures 1 m length. The stones are shaped in a uniform design with the exception of those used for gates, archery slits, and windows. The curtain walls have three layers, outer and inner ashlars sandwiching rubble fill. The walls were built according to the prevailing crusader fortress structural design that characterizes other crusader fortresses in the region, such as Sahyun and Krak des Chevaliers [11]. Deschamps first noted the resemblance of this style to Crusader masonry [5]. Ellenblum maintained further that the masons at Qal’at al-Subayba were locals who served later rulers as well [3].

The Crusader masonry bears clear earthquake marks, but it was not damaged on a catastrophic scale. Although inner sections suffered from substantial destruction (Fig. 4b–d), the curtain walls, in general, survived the earthquake with the exception of large vertical cracks evident everywhere in the eastern and western sections (Fig. 4e–g). Partial structural collapse and stone wreckages found in close proximity to the walls can be observed to the south (Fig. 4h, i). The wreckage piles and scattering radius are smaller than those of the Massive masonry. The wreckage location to the south and the location of the vertical cracks on the eastern and western curtain walls suggest that the surface motion of this earthquake was in a different direction than the earthquake that hit the Massive masonry (i.e., south-north).

Of the inner sections, only the western wall of the Eastern Hall was partially preserved (Fig. 5, see Fig. 2 for location). Therefore, it is the only place in the castle where one can observe the inner compound architecture. Although the compound suffered severe damage, one can clearly identify rib vault (cross vault) elements. Rib vaults are classical Gothic architecture elements and are found in many Frankish constructions across the region [12]. Since these elements are symbolic, representing the shape of the cross [13], they were not adopted for use by the Muslims.

In conclusion, the Crusader masonry has distinct and typical characteristics of Frankish architecture and carries earthquake footprints that are singularly different from those on the Massive masonry. These footprints indicate that the earthquake damaging the Crusader masonry was of lesser severity and that the earth motion was south–north rather than east–west. Based on these observations, it can be concluded that the earthquakes that hit the Massive and Crusader masonries were different and that the earthquake that hit the Massive masonry occurred prior to the Crusader masonry construction.

The Crusaders captured the city of Banias in A.D 1099. During the Crusader reign, the city was the site of fierce fighting and went from hand to hand until it was taken in A.D 1164 by Nur ad-Din Zengī, the Muslim Governor of Damascus. The Ayyubids ruled the region from A.D 1179 to 1260. According to Ellenblum’s theory the local ruler of Banias, Al-Malik al-Aziz Uthman, founded the fortress in A.D 1227 [3]. Ayyubic inscriptions that were found at the fortress attribute constructions primarily to this ruler [5, 14]. At least seven inscriptions have been recorded, of them four are embedded, in situ, in walls or other constructions. Stones with the remaining inscriptions were found on the ground [14]. As the extent of Ayyubic construction is questioned in this work, the term Ayyubic masonry, herein, refers only to construction that bears Ayyubic inscriptions. The inscriptions were characterized and deciphered by Reuven Amitai [14].

The first inscription, dated A.D 1227 (Inscription I, Amitai R. 1989), is located on a curtain wall at the western face of the Southeastern Tower (Fig. 6a and insert; see Fig. 2 for location). The wall appears to be a newer addition to a previously existing, partially ruined section built in Crusader masonry style. The ashlar was made from mid-sized, uneven, roughly-dressed stones. The stones do not fit well and small stones are wedged between the larger ones. This style, resembling Ayyubic fortifications at Hunin, Ajloun, and Msaylha fortresses, is a fine example of the Ayyubid fortification strategy, which was not dependent upon fortified strongholds and placed minor importance on masonry quality [15]. This type of low-quality masonry is considered to be highly susceptible to earthquake damage. Nevertheless, the curtain wall bearing an Ayyubic inscription was preserved and carries no visible earthquake damage albeit the clear earthquake footprints on the Crusader masonry upon which it leans.

The second inscription, dated to A.D 1230 (Inscription V, Amitai R. 1989), is located at the top of the outer face of the Western Tower (Fig. 6b and insert; see Fig. 2 for location). The masonry style is similar to that of the southeastern tower, characterized by uneven, roughly-dressed stones that do not fit very well together. Again, this section bears no visible earthquake footprints.

The third Ayyubic inscription, dated to A.D 1230 (Inscription II, Amitai R. 1989), is located on the western gate of the Northwestern Tower. In contrast with the previously described Ayyubic sections, the masonry at this portion of the site is of higher quality and displays the characteristics of Crusader masonry. It also bears clear earthquake marks (Fig. 6c and insert; see Fig. 2 for location). Based on this observation it is concluded that the Ayyubids carved the inscription on a pre-existing, damaged section of masonry.

The fourth Ayyubic inscription, located above the fountain near the southwestern gate, is attributed to the Ayyubic ruler al-Malik al-Sacid Fakhr al-Din in A.D 1240 (Inscription VII, Amitai R. 1989). The inscription is in an undamaged section of the fortress displaying characteristic Ayyubic masonry. In addition, it was apparently carved on a pre-embedded table, as some of the letters were extended from the table to the frame (Fig. 6d and insert; see Fig. 2 for location). Ayyubic masonry characteristics, described herein, are found at other locations in the fortress that do not carry Ayyubic inscriptions.

The characterization of the earthquake footprints on the different masonry styles at Qal’at al-Subayba indicates that the fortress was hit by two different earthquakes rather than one. These earthquakes were identified as the one of A.D 749 and the one of A.D 1202. Based on these findings, the fortress chronology can be divided into three different periods. Early (prior to the first earthquake), central (between the first and second earthquakes), and late (after the the second earthquake). The Massive masonry represents the early period, the Crusader masonry represents the central, and the Ayyubic and Mamluk masonries represent the late. This study provides firm evidence negating Ellenblum’s Ayyubic Theory. The observation that large portions of the fortress were of Crusader masonry supports Deschamps’ association of the fortress to the Franks [5]. However, the study also provides clear evidence for its ancient origin. Charles W. Wilson, in his A.D 1881 publication, Picturesque Palestine, describes the fortress as ‘one of the strongest fortresses in the East, exhibiting the masonry work of every period from early Phoenician to Crusaders’ [4]. This description accurately encompasses the fortress history.

The question of ‘who built Qal’at al-Subayba’ remains to be resoved. The Massive masonry carries typical Hellenistic characteristics. Therefore, it is suggested that it was founded by the Greco-Syrians. This hypothesis must be further investigated and additional archaeological research is imperative.