The Discovery of the Theater of Akragas (Valley of Temples, Agrigento, Italy): An Archaeological Confirmation of the Supposed Buried Structures from a Geophysical Survey

Abstract

The theater of the ancient city of Akragas has been researched for centuries and, in 2016, a multidisciplinary and multi-scale research work that involved topographic studies, analysis of satellite images, geomorphological characterization of the land, archaeological surveys, and non-invasive geophysical surveys led to its discovery. In this work, a comparison between the archaeological structures hypothesized by geophysical results and the archaeological structure excavated is presented. The area of about 5.500 m2 was investigated using electrical resistivity tomography (ERT). The survey highlighted a series of resistivity highs arranged on concentric semicircles defining perfectly the presence of an articulate building attributable to a theatrical complex of imposing dimensions (diameter of about 95 m). Archaeological excavation led to the identification of the summa cavea with the discovery of foundation-level structures arranged on a semicircle, on which the tiers were located, and cuts in the rock with seat imprints. The overlap of the technical layouts obtained from the documentation of archaeological excavation on the modelled resistivity maps shows the perfect correspondence between the features of the resistivity highs and the ancient structures actually found.

An Extension of the Data-Adaptive Probability-Based Electrical Resistivity Tomography Inversion Method (E-PERTI)

“…The η m function, with η m ∈ [−1, +1], is interpreted as the probability that a resistivity anomaly located in the mth cell, deviating from the reference model, is responsible for the whole set of measured apparent resistivities ρ a,n , within the first-order expansion. The role of probability attributed to η m was motivated as follows, noting that a probability measure Ψ is defined as a function assigning a real number Ψ(E) to every subset E of a space of state U such that [27]…”

“…Many applications of the PERTI approach in near surface prospections are available in literature for solving archaeological research questions such as in the roman city of Aesernia [23], the archaeological park of Pratolino (Vaglia, Florence, Italy) [24], the Bedestan monumental complex (Nicosia, Cyprus) [25], the Temple of Athena in Poseidonia-Paestum (Southern Italy) [26], the theater of Akragas (Valley of Temples, Agrigento, Italy) [27] and the medieval tombstones in Montenegro [28]. The method was also applied for defining faults in Crete [29] and for imaging of the near-surface structure of the Solfatara crater (Campi Flegrei, Naples, Italy) [30].…”

Ground-Penetrating Radar Survey for the Study of the Church of Saint Cosma in Helerito (Tagliacozzo, L’Aquila, Italy)

“…The geoelectrical method, although having slower acquisition times and small invasiveness due to the need to insert electrodes into the surfaces/terrains compared with other methods, is ideal for identifying deep targets providing easily interpretable results in different soils and surfaces conditions. Many examples prove the efficiency of the method for the detection of near-surface archaeological structures, tombstones, and complex buried buildings [3][4][5][6][7][8][9][10][11][12].…”

Ground truth validated 3D electrical resistivity imaging of the archaeological deposits at Arma Veirana cave (northern Italy)

“…ERT is widely used in archaeological studies (Campana and Piro, 2008; Witten, 2017; El‐Qady et al ., 2019). It has been used to investigate site stratigraphy (Papadopoulos et al ., 2006) and the sedimentological architecture (Yogeshwar et al ., 2019), to detect changes in lithology and geology (Laigre et al ., 2012; Scapozza and Laigre, 2014), depositional targets and buried structures (Papadopoulos et al ., 2007; Tsokas et al ., 2009; Supriyadi et al ., 2019; Cozzolino et al ., 2020), to map remnants of past human occupation (Thacker et al ., 2002; Matias et al ., 2006; Papadopoulos et al ., 2010; Berge and Drahor, 2011a,b; Tsokas et al ., 2018), to reconstruct palaeolandscapes (Papadopoulos et al ., 2014) as well as to detect offshore archaeological features (Sarris et al ., 2014; Tonkov, 2014; Simyrdanis et al ., 2015). ERT is also widely used to choose the most promising areas to excavate (Piroddi et al ., 2020).…”