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Abstract(s)
In summer of 2022, the Berlin–based company cmp in cooperation with SOT Prospecció Arqueològica, Barcelona (Spain),
realized the first large–scale geophysical prospection campaign in the Roman city of Conimbriga (Condeixa–a–Nova,
District of Coimbra, Portugal). Conimbriga has been a classified National Monument since 1910 and is one of the most
important archaeological sites in Portugal. The site was first settled in the Iron Age and later occupied by the Romans in
the 1st century BC. After destruction in the 5th century BC, only low settlement activity is documented, until the place was
completely abandoned and used for agricultural purposes and as a quarry. Archaeological research of the site began in
the 19th century and has continued to the present day. Excavations have revealed a wealth of information about the
town, including large parts of its layout, monumental buildings, and artefacts. So far, the geophysical prospection was
used only on small sections of the site, starting already in the 1960s, when first magnetic and electric surveys were
carried out. The campaign of 2022 was the first large–scale application of both magnetic and georadar methods in
Conimbriga. During a 5–day campaign, an area of 8 hectares was covered with magnetic measurements using the cmp 7–
probe fluxgate gradiometer array combined with a GNSS–RTK positioning system. At the same time, an area of 1.5
hectares was investigated by use of the IRIS HI–MOD (IDS) system equipped with five 600 MHz antennas, also combined
with a GNSS–RTK system. In addition, several soil samples were taken in order to determine their magnetic susceptibility
and the electrical conductivity. The most important result of the survey campaign is the understanding that th e
geological and archaeological conditions in Conimbriga are extremely challenging for both, magnetic and GPR
prospection. Low contrasts in magnetic susceptibility and high clay content of the soil result in noisy and diffuse
geophysical data. Moreover, geological and surface conditions change throughout the site. The areas first studied were
located in the Vale Norte (North valley) where remains of Roman houses were localized. To the east of the already known
amphitheatre other building remains, and a complex stratigraphy, were identified. They could be related to another
theatre, which is suspected to be there. Subsequently, the area inside the late–imperial city walls was investigated. The
magnetic data set covers almost the entire accessible area to both sides of the forum and the southern baths. An area of
about 9,000 m², located in the eastern part of the city was covered with both, magnetic and GPR measurements. Despite
the limitations, this large–scale data set allowed to identify monumental building complexes in all parts of the intramural
area and to distinguish city quarters and ancient infrastructure. It has to be stated that the presented interpretation of
the geophysical data is a first attempt to translate the diffuse geophysical data into archaeological information. It is
based primarily on the geophysical data itself and the available a–priori information. Certainty about the reliability of
this interpretation can be gained by verifying the proposed interpretations through targeted archaeological excavations
by a discussion on the plausibility of the interpretation. The report ends with considerations for planning future
geophysical prospection projects in and around Conimbriga.
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Pedagogical Context
Citation
Meyer, Cornelius 2023: Geophysical prospection in the Roman city of Conimbriga (Condeixa–a–Nova, District of Coimbra, Portugal). Umpublished report. Berlim: cmprospection.