Challenges and Opportunities in Multi‐Method Integrated Geophysical Prospection of Buried Building Remains at the Sanctuary of Olympia

ABSTRACT Ancient Olympia was one of the most important sanctuaries and the venue for the Olympic Games in Greek and Roman times. Its remains are located in the Olympia Terrace (Peloponnese, Greece) at the present‐day confluence of the rivers Alpheios and Kladeos at the base of Mount Kronos. Olympia is situated on the northern fringe of the Makrisia Basin. Due to its position between the two rivers, the sanctuary was covered by several metres of sediment (mainly silt and sand) after its abandonment, which complicates exploration and excavation. This raised the following questions: (i) Are there more buildings connected to the Sanctuary than previously known from excavations, and if so, (ii) how and (iii) with what resolution can such deeply buried structures be detected using geophysics? During geophysical and geoarchaeological campaigns in 2021 and 2023, an integrated multi‐method approach containing electromagnetic induction, electrical resistivity tomography and shear‐wave seismic measurements, aiming specifically at looking below the thick sediment cover, was performed between the excavated parts of the sanctuary and the southwestern edge of the original Olympia Terrace. A multi‐phase filter was developed to separate the electromagnetic response signal of the Mediterranean olive grove from subsurface features. The chosen prospection approach was evaluated in terms of its resolution and ability to image ancient building remains at depths, that cannot be reached by commonly used geophysical methods in archaeological prospection. The integrative analysis of the results, in addition to a large‐scale inversion of the electromagnetic induction data, establishes more detailed insight in a recently described building structure and the course of the levee belonging to an embankment of the Kladeos river and containing the Kladeos wall.