Geophysical and Photogrammetric Measurements at the Fortezza Castle of Rethymnon (Crete)

In 2014, the GeoSat ReSeArch Lab of the Foundation for Research and Technology (FORTH) explored the subsurface structure in three areas on the Fortezza castle in Rethymnon (fig. 1). The first target of investigations (Area 1) was the area of the Hellenistic monuments in the bastion square of St. Lukas. Part of this has been already explored by excavations by the 15th Ephorate of Prehistoric and Classical Antiquities that brought to light remains of houses of the Hellenistic period, preserved under the buildings of the Venetian, Ottoman and modern times. The architectural remains seem to have been built with elaborate masonry and sections of a bathroom and a yard were also uncovered. The continuation of the excavation in this section of the site is almost impossible as extensive backfilled soil was deposited during the Venetian period and its removal would cause issues in the integrity of the fortification walls. In the context of restoration works in the SE part of the Fortezza, and more particularly in the area of the bastion of St. Paul and the Cortina between the bastions of St. Paul and St. Lukas (Area 2), geophysical research was carried out to address basic questions related to the construction of the fortress. The aim was to check if within the backfilling of the bastion and the Cortina there are supporting (transverse) walls, in accordance with the records of the Venetian archives. The third locus (Area 3) of the geophysical experiments was outside of the fortress in the western foot of the hill (toponym Chochlada), where some rock-cut shipsheds, most probably of the Hellenistic period, have been identified. The goal of the geophysical surveys carried out through the application of the GPR and ERT methods was to try to trace most of the parts of the E-W shipsheds projected from the foot of the hill towards the sea. The investigations, coupled with a drone aerial photography method, made it possible to reconstruct photogrammetrically this particular part of the Fortezza.