HIGH FREQUENCY GPR INVESTIGATION AT KAHAL GRANDE, GREECE

Kahal Grande, located on the island of Rhodes, is thought to have been established in the late 1480s under Ottoman rule. Due to the constant change in rule and thus architectural features, the ruins of the synagogue that exist today may be overlying several different renditions of past synagogues.

With the use of ground penetrating radar (GPR) at a frequency of 225MHz, the subsurface of two grids was captured. The first grid ran 12 m x 10 m with the starting point (0,0) at the synagogues southwest corner. With a total of 40 lines at every quarter meter of the grid running south to north the entirety of the synagogue floor was investigated. The second grid with the dimensions of 16 m x 11 m was shot with a starting point (0,0) in the northwest corner and ran from west to east. This grid consisted of 46 lines shot at every quarter meter.

Processing of the data resulted in numerous anomalies approximately a quarter meter beneath the surface. Initially, several of these abnormalities were dismissed due to surface irregularities during data collection caused by the destruction of the synagogue. Other anomalies in the results reaffirm the location of a potential wall running the length of grid one in the western side of the synagogue. An anomaly located roughly at (8,4) on the first grid and (3.5,8.5) on the second grid, between what used to be the bemah and the ark, cannot be explained without further investigation. The interesting aspect of this particular anomaly is that it is located beneath a 1.75 m² pattern on the surface. This leads to the interpretation that this area was meant to be marked by the pattern and represents an important underlying feature within the synagogue. Some possible explanations for this feature include the idea of a time capsule from the practicing Jewish community prior to the synagogue’s destruction or a temporary storage area for previously used Torah scrolls known as a “genizah”. This high frequency GPR work at Kahal Grande can lead to a better understanding of the multiple layouts of the synagogue and give historians a more in depth look at how the Jewish community of Rhodes practiced their faith throughout it’s decades of use.