© 2010 European Association of Geoscientists & Engineers 433 Near Surface Geophysics, 2010, 8, 433-439 doi:10.3997/1873-0604.2010030 * rizzo@imaa.cnr.it which was made by the Nasca, one of the most important and evolved pre-Colombian civilizations (Silverman 1993). The archaeological structures to be unearthed are walls, plat- forms and terraces in adobe. The excavations carried out during the last 25 years have shown a complex stratigraphy composed of overlaid structures, refilled with earth, vegetable material and offerings. All these materials are covered by alluvial deposits. In this context, the detection of buried remains is very critical due to i) the complex archaeological stratigraphy and ii) the low geophysical contrast between adobe structures and alluvial sub- soil. To cope with these issues a multi-method geophysical approach was adopted during two different field trips (April 2008 and November 2008) carried out in an area located near the Templo del Escalonado (see Figs 1 and 2). In order to detect buried structures, two different techniques were used: i) geomagnetic with a gradiometric system and ii) ground-penetrating radar (GPR). Archaeo-geophysical methods in the Templo del Escalonado, Cahuachi, Nasca (Peru) Enzo Rizzo 1* , Nicola Masini 2 , Rosa Lasaponara 1 and Giuseppe Orefici 3 1 CNR-IMAA, Institute of Methodologies for the Environmental Analysis, C.da S.Loja, 85050 Tito Scalo (PZ), Italy 2 CNR-IBAM, Institute of Archaeological and Architectural Heritage, C.da S.Loja, 85050 Tito Scalo (PZ), Italy 3 Centro de Estudios Arqueológicos Precolombinos (CEAP), Nasca, Peru Received December 2009, revision accepted July 2010 ABSTRACT The application of geophysical prospection methods to detect earthen remains is one of the major challenging issues to be addressed in archaeological investigations. The subtle geophysical contrast between earthen buried remains and the surroundings makes the detection of archaeological features very difficult. In this paper, we address this challenge using a multi-technique approach. The inte- gration of different geophysical methods has been used to identify archaeological remains in Cahuach, Peru, which is the largest adobe ceremonial centre in the world. The investigations herein presented are focused on two different geophysical campaigns carried out in 2008 in an area of the Templo del Escalonado, which is highly representative of the whole archaeological site. It is a desert environment where the archaeological features are covered by sand and alluvial material. The geophysical prospection, required by the archaeologists to guide excavation planning, was performed using both ground-penetrating radar (GPR) and geomagnetics with a gradiometer sys- tem. The first allowed the detection of significant anomalies, the latter confirmed the presence of these anomalies and also provided additional features not visible from GPR. Trial excavations were carried out in correspondence of some anomalies. The archaeologists unearthed a ceremonial offering in correspondence of an anomaly detected using both GPR and geomagnetic methods. Moreover, an altar and precious archaeological materials were discovered in the area characterized by a magnetic anomaly. From an archaeological perspective, these findings were very significant, because they enabled us to cast new light on the Templo del Escalonado. From a geophysical perspective, our results pointed out the high potentiality of magnetic and GPR techniques to detect, investigate and document adobe archaeological remains in a desert envi- ronmental setting. INTRODUCTION The detection of buried adobe (earthen) structures by using non- invasive techniques, such as geophysical prospection, is a com- plex and crucial challenge. It is complex because of the subtle physical contrast between earthen remains and the surrounding subsoil. It is crucial because of the long and widespread use of earthen materials by several civilizations mainly in arid and semi-arid lands. In the coastal regions of Peru, the adobe archi- tecture is well preserved due to the hyper-arid climate, as in the case of the Mochica remains on the northern coast, or the Nasca buildings and monuments on the southern coast (Moseley 2001). Our efforts to address this challenge are presented in this paper and discussed for an area selected from within the ceremo- nial centre of Cahuachi (Orefici and Drusini 2003; Orefici 2010),