las in the Alban Hills, especially in the Albano
Laziale town area. Some of these were great lux-
ury buildings, such as the Roman villa discovered
in the Cavallacci area, in Via Verdi. The villa
probably belonged to a member of the imperial
family because, during excavations, a large quan-
tity of fine-quality marble emerged. The Villa ai
Cavallacci was discovered in 1975 but the archae-
ological investigation (performed by the Civic
Museum of Albano Laziale) started only ten
years later, in 1986 and is still in progress. Only a
small part of the archaeological site was excavat-
ed and the aim of the geophysical survey was to
realize a spatial reconstruction of shallow buried
walls and rooms, to define new possible excava-
tion sites. The digging has revealed many mason-
ry structures, rooms with mosaic and polychrome
marble floors. The structure, which was built to-
wards the end of the republican period, reached
the height of its magnificence during the Tiberius
era and in III century A.D. under Severus age. It
was inhabited until V century A.D. (Chiarucci,
1990). Starting from the end of the III century
A.D. the building was used only as a burial place
until the residential building, already neglected
and quit, became a country villa.
3. Geophysical methods
The primary goal of this survey was the
identification of targets of potential interest in
an area partially investigated by archaeologists
in previous excavations. To obtain high resolu-
tion results in a short time, a preliminary mag-
netic analysis and a large step GPR grid were
carried out on the areas indicated by the archae-
ologists. Then some new GPR and geoelectrical
profiles were performed to obtain new details
on the most interesting areas identified by the
preliminary investigation.
3.1. GPR survey
The GPR method is based on the reflection
of an electromagnetic wave due to one or more
discontinuities in the media dielectric proper-
ties. The main physical factor that can generate
a reflected radar wave is the dielectric contrast
between different media. Buried shallow walls
and holes generate a good contrast in the field
of dielectric properties providing a possible and
resolvable target for the GPR method (Annan
and Cosway, 1992; Jol and Smith, 1992; Ben-
son, 1995; Daniels, 1996; Basile et al., 2000).
Analysing the direct waves on a WARR test
dataset produced a value of about 5.7 for the di-
electric constant of the surrounding medium (a
silty sand) using an averaged electromagnetic
wave speed of about 0.125 m/ns. The buried
structures were essentially made of limestone
blocks and marble floors; both showed a good
dielectric contrast from surrounding medium
properties.
GPR profiles were mainly carried out along
NW and SW directions, as shown in fig. 2, by
GSSI Sir10B instrumentation equipped with a
400 MHz monostatic antenna.
Unfortunately, many anthropic obstacles
(excavation scraps, power lines, etc.) hold up a
regular spaced acquisition greed. For this rea-
son, we employed a two step profiling method.
First, lines were acquired 3 m spaced and then,
according to the results of the recorded GPR
profiles, they were thickened as much as possi-
ble only where it was needed.
The acquired profiles showed many archaeo-
logically interesting anomalies. Figure 3 shows
the position of some of them by A, B and C box-
es, where red and green indicate anomalies
linked to buried walls and flat high energy reflec-