The Etruscan and Roman site of Montetosto is located 4 km to the west of Caere, along the monumental road (Fig. 1) that connected the Etruscan city to its main port at Pyrgi (Colonna, Reference Colonna2000, Michetti Reference Michetti, Baglione and Michetti2015). Until 1962 the site was known only for the visible tumulus – presently the largest known in Etruria – excavated by Raniero Mengarelli between 1924 and 1929 (Mengarelli, Reference Mengarelli1927, Rizzo, Reference Rizzo1989).

Fig. 1. The Caere–Pyrgi road and the location of Montetosto.

Excavations carried out between 1965 and 1969, following the fortuitous recovery of some architectural terracottas, led to the discovery of a square building (with regular sides of 54 m in length), which was immediately compared to recently discovered palatial structures at Murlo and Acquarossa (Colonna, Reference Colonna1985). The sacred function of the building in the period 6^th–2^nd century BC could be understood due to the recovery of both architectural and votive terracottas. In the late 2^nd century BC the function of the complex shifted from sacred to profane.

Despite limited field research, the Montetosto sanctuary has played a crucial role in scientific debates of the last forty years. According to the reconstruction first proposed by Colonna and subsequently widely accepted, it was erected in the place where the Phocean prisoners were stoned to death after the Battle of Alalia (540 BC); its palatial shape probably hints at the aristocracy's responsibility for the murder and it is ideologically connected with the monumental, earliest tumulus (Belelli Marchesini, Biella, Michetti, Reference Belelli Marchesini, Biella and Michetti2015, 147–9, 154).

The finds and data of the excavations of the 1960s were fully published in 2015 (Belelli Marchesini, Biella, Michetti, Reference Belelli Marchesini, Biella and Michetti2015, 147–9, 154 with previous bibliography) and whilst a better understanding of the site has emerged several questions still remain. In particular the layout of the building itself as well as the possible presence of further structures, either below or in close proximity. In addition, the sanctuary needed to be better understood in its wider topographical context, both considering its physical connection with the Caere–Pyrgi road and its visual link with the monumental tumulus. Therefore in 2018 a new phase of investigations began through a joint research partnership between the Sapienza Università di Roma (Dipartimento di Scienze dell'Antichità) and the British School at Rome.

A short season of geophysical survey was conducted in March 2018 in close collaboration with the Soprintendenza Archeologia, Belle Arti e Paesaggio per l'area metropolitana di Roma, la provincia di Viterbo e l'Etruria Meridionale. An area of 1.07 ha was surveyed between the Montetosto tumulus and the eastern edge of the previously excavated building (Fig. 2).

Fig. 2. The geophysical survey results from Montetosto with the magnetometry data (left) and interpretation of major features (right).

The magnetometry surveyFootnote ¹ highlighted the presence of a substantial series of additional walls and features in the eastern sector of the complex (Fig. 2: 1) in an area not fully explored in the excavations of the 1960s. Indeed, the supposed absence of structures in the central part of the building led to the recognition of a central courtyard and consequently to the definition of a sanctuary in the form of a palace (Colonna, Reference Colonna1985, 193), which still remains unique in the panorama of Etruscan sacred structures.

In the northern part of the survey area the magnetometry precisely mapped the perimeter of the west side of the tumulus which is now buried (Fig. 2: 2), confirming a diameter of 65 m. On the exposed eastern side of the monument several red tuff slabs which formed part of the base of the monument were visible.

The route of the Caere–Pyrgi road between the tumulus and the sacred building was suggested by the topographical surveys carried out in the 1960s. The fieldwork indicated the general trajectory of the road, but it was clear that in the vicinity of Montetosto it had already undergone substantial destruction (Giuliani, Quilici, Reference Giuliani and Quilici1964, 8). The magnetometry has highlighted the presence of two parallel anomalies to the north-east of the sanctuary which may be associated with the Caere–Pyrgi road (Fig. 2: 3–4); however, these features need to be further explored to confirm the hypothesis.

The geophysical survey at Montetosto has clearly demonstrated the need for further researchFootnote ² in the area, both with further geophysical prospection in the adjacent fields and for excavation in the eastern sector of the sacred building.