The castle of Arsur, located near the northern edge of the town of Arsur, has been the subject of extensive research and ongoing excavations by the Apollonia-Arsuf Excavation Project team (Area F; Zeischka-Kenzler et al. 2018, and see a brief historical background therein and additional references). The construction of the castle began in 1241 CE by the Ibelin family, as part of the rebuilding of the town, which served as administrative center of a seigneury. In 1261 CE, the castle was leased to the Order of St John (Hospitallers), who occupied the site and refortified both the town and castle. Following a siege imposed in March–April of 1265 CE by Baybars, the fortified town and castle were destroyed by the Mamluks; no permanent settlement has occupied the site ever since.
 
Excavations in Area F (Fig. 1), which began in 1998, have yielded considerably large and well-dated assemblages of Crusader-period artifacts, including pottery (Tal 2011), glass (Jackson-Tal and Tal 2013), metal artillery (Ashkenazi, Golan and Tal 2013), coins (Tal, Kool and Baidoun 2013), lead tokens (Kool and Tal 2015) and animal bones (Pines, Sapir-Hen and Tal 2017), as well as studies on its maritime installation (Mirkin, Cvikel and Tal 2016; Mirkin 2018) and architectural elements (Shotten-Hallel, Yohanan and Tal 2020).
These recent archaeological investigations have uncovered evidence of both the castle’s construction phase in 1241 CE and the phase of modifications and refortification that followed its lease to the Hospitallers in 1261 CE. These two major enterprises left an architectural blend, which the 2018–2020 excavation sought to better understand. The aim of this project was to examine the extent of the functional modifications and the architectural interventions carried out by the Hospitallers. Additionally, it sought to identify the location of the castle chapel by analysing the architectural finds and reconstructing their original location and setting, as most of them were found in debris of the castle destruction.
The 2018–2020 excavations continued the 2009, 2010 and 2012 excavations in the western part of the castle (the ‘western façade’), where at least three halls—northern, central and southern—were identified during the 1998-2000 survey and excavations of the castle. The three halls are only partially preserved due to stone robbing throughout the centuries and erosion from the disintegration of the sea cliff (Figs. 1, 2). These halls delineated the central courtyard of the castle on the west. A massive polygonal structure (the ‘donjon’) projects eastward from the central hall into the courtyard. Abutting this massive structure on the south is a wide and massive staircase that ascended westward from the courtyard.
 
The 2018–2020 excavations focused on unearthing two of the halls of the castle’s ‘western façade’, the central and northern halls (Figs. 2, 3), where it was hoped to find answers to the two leading research questions of the project; the southern hall was left for exploration in future field seasons. Although only scarce remains of the chapel have survived in situ—it was probably destroyed by the Mamluks and suffered from the post-Frankish systematic stone robbing at the site—several indications pointed to its location in this structure, probably on an upper story, allowing for the apse to be located in the eastward-projecting ‘donjon’. These include the hall’s plan within the ‘western façade’, the polygonal plan of the ‘donjon’ and the location and direction of the adjacent staircase, as well as the numerous architectural and sculptural elements discovered since 2009 within the debris of the halls comprising the castle’s ‘western façade’ (Shotten-Hallel, Tal and Yohanan 2020).
 
The central hall. The excavation in the central hall yielded two superimposed floors on its ground level, reflecting the two periods of construction in the castle’s history (Fig. 4): a flagstone pavement, probably constructed in the 1240s, covered by a plaster floor, apparently from the Hospitaller occupation. This upper floor was associated with several additional architectural alterations carried out by the Hospitallers, such as narrowing the hall’s openings on the south and on the north. Such alteration may reflect the adaptation of spaces in the castle to their way of life and needs. For example, the Hospitallers relied on supplies—both commodities and personnel—from the sea, whereas the members of the nobility class, who occupied the castle before 1261, were dependent on supplies and services from the nearby town.
A threshold uncovered in the southwestern corner of the hall (Fig. 5) allowed us to identify for the first time an outer ramp (Fig. 6), which probably led from the central hall to the seashore. Ascribing the threshold to the 1241 CE phase and understanding its position were aided by a typology created for all the thresholds in the castle, and their classification according to construction phase (1241 or 1261 CE) and type of space (interior or exterior). We hope to confirm this assertion in a future excavation to the south of the threshold.
The small finds from the destruction level of the upper floor in the central hall, dated to 1265 CE, include pottery forms that date mainly from the thirteenth-century CE (Fig. 7), glass vessels and windowpane fragments, of both monochrome and grisaille stained glass (Figs. 8, 9), and several coins. Samples of mortar, plaster and plaster floors collected from several points are currently being analyzed and dated. Burnt wooden beams preserved on the upper floor may also be associated with this level of destruction. An analysis of similar beams in other parts of the castle identified the wood as cedar (Cedrus libani).
 
The northern hall. The excavation in the northern hall (c. 8 × 20 m; Fig. 10) uncovered the remains of a stable. A plastered stone shelf (preserved length c. 8 m, width 0.4 m, height 0.8 m) was set along the eastern wall of the hall. Incorporated in the shelf were hewn tethering holes and on its top were the remains of plastered troughs. Drainage holes were sunk into the plaster floor of the hall, indicating the collection of liquids, most likely horse urine.
While the western wall of the hall collapsed, the inner face of the eastern wall displays an uneven quality of construction: its southern half is well-built, while its northern half is poorly constructed. This may suggest that the northern part of the hall was open to the sky. Several ashy patches found on of the hall’s plaster floor attest to cooking activities during the Mamluk siege of 1265 CE, when the site became a refuge for the Knights Hospitaller, as well as for inhabitants of the town and seigneury.
 
Architectural elements. Several architectural and sculptural elements were found in the fills above the plaster floor in the central hall (see Fig. 4). The study of these, along with over seventy similar architectural elements uncovered in previous excavation seasons in the castle, made it possible, for the first time, to propose a reconstruction of the chapel’s external layout following renovations by the Hospitallers, as seen in Figs. 11 and 12, and to distinguish between the different phases of construction. Furthermore, they attest to its exquisite architectural language, as exemplified by a unique jamb capital, which probably originated from the portal of the principal entrance to the chapel (Fig. 13), as well as by the fragments of the stone window frames and the stained-glass windowpanes that probably came from a rose window.
Along with the Frankish architectural and sculptural elements were Byzantine architectural element, suggesting that spolia from Byzantine-period structures (Fischer, Tambakopoulos and Maniatis 2018) were incorporated in secondary use in the thirteenth-century CE construction. Various Byzantine-period spolia were also found in previous excavations in the courtyard and the moat of the castle, and some were incorporated in the post-Frankish wall, built against the inner face of the eastern wall of the central hall (W2852; see Fig. 1).
 
The excavation results of the 2018–2020 seasons, like those of the previous seasons, provide a better understanding of the site, and specifically of its social and occupational history in the late Crusader period. The analysis of the finds resulted in a system of differentiating the secular characteristics of the castle, built by the Ibelin family in the 1240s, and the religious and military adaptations affected by the Hospitallers between 1261 and the siege of 1265 CE. The excavations exposed invaluable artifacts and architectural elements that contribute to our understanding of the architecture of the castle’s chapel. The remains of stone window frames and the stained-glass shards seem to indicate that this chapel had a rose window—a rare find from the thirteenth-century CE Latin Kingdom of Jerusalem. We hope to uncover many more similar fragments of glass windowpanes in the future seasons, allowing for a fuller and more substantiated reconstruction of this and other windows. Finally, the uncovered architectural and sculptural elements will be used in the preservation and conservation of the castle’s ‘western façade’, an intervention that will include processes aimed at slowing down the erosion and disintegration of the sea cliff.