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XI/2/2020
INTERDISCIPLINARIA ARCHAEOLOGICA
NATURAL SCIENCES IN ARCHAEOLOGY
homepage: http://www.iansa.eu
Geophysical Survey of the Hillfort Staré Zámky near Brno-Líšeň,
Czech Republic
Peter Miloª
*
, Tomáš Tencerª, Michal Vágnerª, Michaela Prišťákováª, Igor Murínª
a
Institute of Archaeology and Museology, Faculty of Arts, Masaryk University, Arna Nováka 1, 602 00 Brno, Czech Republic
1. Introduction
This article discusses the results of geophysical surveys
carried out at the archaeological site of Staré zámky near
Brno-Líšeň, Czech Republic. The research, undertaken
within the framework of the project “Early Medieval
hillforts in the light of non-destructive investigation”, as
the name suggests, aims to extend our knowledge about
Central European Early Medieval fortifed sites using a wide
range of non-invasive prospection methods. The main task
was to answer questions related to the layout of the features
inside the hillforts and their immediate surroundings,
as well as the extent and density of inhabitation and the
nature of the fortifcation systems. Staré zámky proved to
be a suitable example site to demonstrate the contribution
of various geophysical prospecting methods in gaining new
knowledge about an area that has been already intensively
archaeologically excavated in the past.
2. The site and its context
The poly-cultural site “Staré zámky” is located approximately
1.5 km to the northeast of the centre of Brno-Líšeň suburb.
It is situated on a prominent rocky promontory formed by
conglomerates, oriented with its longer axis in a northwest
to southeast direction. Approximately in the middle of the
promontory there is a narrow, approximately 30 m wide,
neck. From here, the promontory extends towards the
southeast into an irregular isosceles triangle with a total area
of approximately 4 ha. The northern, eastern and southern
sides of the promontory are bordered by steep, partly-rocky
hillsides (elevation approximately 60 m), which are wrapped
around by a small watercourse called “Říčka”. From the
western side, the promontory is bounded by a steep ravine
that rises towards the northwest before becoming a gently-
sloping plateau.
The oldest traces of settlement can be dated back to the
Neolithic period. However, archaeological excavations
failed to identify a single settlement feature from this
period. Signifcantly more-intensive settlement came with
Volume XI ● Issue 2/2020 ● Pages 183–195
*Corresponding author. E-mail: milop@post.sk
ARTICLE INFO
Article history:
Received: 7
th
May 2020
Accepted: 13
th
October 2020
DOI: http://dx.doi.org/10.24916/iansa.2020.2.4
Key words:
Early Medieval Period
hillfort
non-destructive methods
magnetometry
ground-penetrating radar
electrical resistivity tomography
ABSTRACT
The aim of this paper is to present the results of geophysical surveys at the Staré zámky site near
Brno-Líšeň, which were carried out in 2019. Electrical resistivity tomography, georadar survey and
large-scale magnetic prospection were all carried out there. The primary task of the frst two methods
was to investigate the inner structure of the still-existing ramparts and to identify their individual
structural elements. The magnetic survey focused on the identifcation of areas where potential
archaeological features can be found – together with the identifcation of previously-unknown
fortifcations. The surveys were successful: we have found numerous settlement features from diferent
phases of settlement, an early medieval cemetery and fortifcations of various types, sizes and state of
preservation. The results of previous archaeological research of the site played an important role for
interpretation of the geophysical data. Together these results provide important insights into the study
of the complex fortifed settlement of Staré zámky. Despite our results, some questions which cannot
be answered by geophysical research alone remain unanswered.
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the Eneolithic period. At that time, there was a settlement
protected by a rampart and ditch (Medunová-Benešová,
1964). Further traces of settlement have been found from
the Bronze and Iron Ages, as well as from the Roman and
Migration periods.
The largest growth in settlement came during the
Early Medieval Period. The oldest evidence of the Early
Medieval settlement comes from the 7
th
to 8
th
century, when
in addition to the material fnds, several housing features
and remains of fortifcations in the form of a wooden
palisade have been found (Procházka, 2009, pp.152–157;
Staňa, 1972, pp.111–114). The large area (approximately
4 ha) of the promontory was surrounded by a wood-
earth structure with a frontal stone wall in the 9
th
century
(Procházka, 2009, pp.152–159; Staňa 1972, pp.115–117).
Its remains are still preserved on the northern and eastern
side of the promontory, which can be described as the
acropolis of the hillfort. Behind the narrow neck of land
to the northwest of the acropolis was a bailey (“Bailey I”),
which was approximately 1 ha in size and triangular in
shape. From the northwest it was surrounded by a rampart,
possibly of a stone structure, but the perimeter of the
promontory was apparently not protected (Procházka,
2009, p.157; Staňa, 1972, p.136). Further to the northwest
there stood another bailey (“Bailey II”), which was
fortifed by a massive earthen rampart with a ditch on the
north-western side. The preserved rampart itself is over
300 metres long. In the south, it emerges from the forest to
a feld where it has been ploughed up, but it continues in
the form of an indistinct terrain wave towards the present-
day Líšeň cemetery, where its further course then becomes
problematic (Procházka, 2009, p.157; Staňa, 2000, p.201).
The size of Bailey II is not clear to us, but according to the
known facts and confguration of the terrain, we estimate
it to be approximately 10 ha.
Associated with the existence of an Early Medieval
hillfort, there was are also a large number of
archaeologically-recorded residential features excavated,
both habitable and economic (Staňa, 1972; 2000, p.201).
In the north-western part of the acropolis it is considered
that there was a fenced area, which Staňa (1972, p.139)
describes as a magnate court. Within Bailey II, part of
a skeletal burial ground (dated to the 9
th
century) has been
uncovered (Poulík, 1948–1950, pp.103–104). At the turn of
the 10
th
century, the fortifed settlement was hit by a large
fre, which may be associated with a violent invasion (Staňa,
1972, p.154; 2000, p.201). Sometime at the beginning of
the 10
th
century, shortly after the demise of the hillfort,
a smaller fortifed settlement was built at the acropolis
area. Subsequently, during the 10
th
century, a short “hiatus”
in settlement (Kalčík, 2013), or a period of only sparse
settlement of the site has been predicted (Procházka
et al.
,
2011, p.497; Staňa, 1972, pp.157–158; 2000, pp.203–206).
During the second half of the 11
th
century, settlement of
the site started to decline (Kalčík, 2013, pp.234–235; 2015,
p.193).
3. Archaeological excavation and geophysical research
of the hillfort
The Staré zámky site was archaeologically intensively
investigated in the past. In 1863, several human skeletons
and archaeological artifacts were found during ploughing. In
1890–91, a local archaeologist, Martin Kříž, conducted the
frst excavation on the site. A total of 40 detection pits, two
124-metre-long probes and several cuts through the rampart
were carried out (Poulík, 1960, p.132). During 1948–49,
under the leadership of Josef Poulík, Bailey I and the neck
of land between Bailey I and the acropolis of the hillfort was
excavated. In total, an area of approximately 2250 m² was
uncovered. A part of the 9
th
century skeleton burial ground
was also excavated (Poulík, 1949). Between 1953 and 1965,
the most extensive stage of excavation so far was carried
out, uncovering an area of 5250 m². On the promontory
of the hillfort, excavation cuts on the perimeter wall. The
excavation also uncovered the remains of prehistoric and
Early Medieval settlement in the form of housing features,
ditches and the rest of two routes dated to the Bronze Age and
Early Medieval period (Benešová, Staňa, 1959, pp.166–174).
Since then, no archaeological excavation has been carried
out on this site. However, recently, the number of fndings
obtained with the help of metal detectors originating from the
area of the hillfort, or its immediate vicinity, has substantially
increased (
e.g.
Vachůt
et al.
, 2013).
More than half a century has passed since the last
excavations were conducted on the site. The fndings were
partially processed, and the old research has been reviewed
and summarized (Kalčík, 2013; 2015), but no new information
has been added that could broaden our knowledge. The
geophysical survey planned for this site in 2019 was to
erase this shortfall. Given the curtailed possibilities for
archaeological methodology, such as the limited size of the
surveyed area, or the costly and time-consuming excavation
of the fortifcations, the use of geophysics was justifable.
A geophysical survey enables the identifcation of subsurface
structures of an archaeological nature in a relatively short
time. Moreover, as it is non-destructive, it leaves the site
under investigation intact for further research in the future.
The aim of the geophysical measurements at Staré zámky
was to broaden our knowledge of the intensity and character
of the settlement, as well as the fortifcation system of
the hillfort. Electrical resistivity tomography (ERT) and
georadar (GPR) survey were carried out, focusing on the
preserved remains of the hillfort’s fortifcation elements –
the ramparts and ditches. There was also a magnetic feld
survey, which focused on the accessible area in the acropolis
and both bailies.
The role of ERT and GPR prospection was to identify the
internal structure of the rampart fortifcations, or to focus on
the identifcation of adjacent ditches and determination of
their potential extent and depth. A visual survey identifed
the two most suitable places. The frst one was located on the
eastern edge of the acropolis and the second in the northern
part of the outer rampart of Bailey II (Figure 1).
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185
For the purpose of georadar surveying, a X3M Ramac
georadar (Geoscience AB Malå), with two shielded antennae
with a central frequency of 250 and 500 MHz, was used.
On the eastern edge of the acropolis, due to the dense
vegetation, only a single profle approximately 18 m in size
was measured. On the outer rampart of Bailey II only one
46 m long profle was measured, the surveyed area being
4×30 m. The spacing between the individual measurement
lines was 0.5 m (Figure 1). GPR data collected throughout
the area were evaluated using ArchaeoFusion software
(University of Arkansas), Easy 3D software (Geoscience AB
Malå) and GPR Slice software (Geophysical Archaeometry
Laboratory). Horizontal time/depth cuts were exported in
raster form (JPEG) to ArcGIS (ESRI), where they were
georeferenced, interpreted and the identifed anomalies
further digitized into a vector plan. Vertical time/depth
cuts were processed using RadExplorer software (v. 1.42;
Geoscience AB Malå) and vectorized in Adobe Illustrator
CS6.
The ERT prospection was performed using the ARES
850W apparatus (GF Instruments Brno). At the eastern
edge of the acropolis a 26-metre-long profle was measured.
On the outer rampart of Bailey II, a 47-metre-long profle
was measured (Figure 1). Three types of confgurations
were used – Wenner, Schlumberger and dipole–dipole.
RES2DINV software (GEOTOMO, Malaysia) was used
for data processing, where both the extreme values were
removed, and the apparent resistivity values were inverted
to the actual resistivity values. Topographic correction was
applied to the resulting data and the resulting model was
created showing the real distribution of the specifc electrical
resistivity in the given profle.
Magnetometry is the most suitable geophysical method for
resolving issues related to settlement activities, as it is able to
explore large areas in a small amount of time and at the same
time identify a wide range of archaeological structures. The
total area investigated at the Staré zámky hillfort reached
12.01 ha (acropolis: 3.36 ha; Bailey I: 0.81 ha; Bailey II:
6.87 ha; area outside of fortifcation: 0.97 ha; Figure 1). The
survey was carried out with a fuxgate magnetometer LEA
MAX (Eastern Atlas, Germany). The instrument is designed
as a gradiometer. Due to the fat terrain it was possible to
use ATV mode (the instrument was pulled by a quad). Ten
fuxgate probes (FEREX CON 650, Foerster, Germany)
confgured 0.5 metres apart were used for the measurements.
The density of the magnetic measurements was 0.5 m on the
X axis and 0.1 m on the Y axis (measurement direction). The
measured data were collected together along with spatial
information from the GNSS receiver – Trimble R-10 model 2
(Trimble, USA). Measurement data were processed using the
standard procedure in LEAD2 program. The magnetic feld
intensity map (magnetogram) in nanoTesla (nT) units was
then smoothed by averaging. ArcGIS Desktop 10.7 (ESRI)
software was used to present and interpret the results.
Figure 1.
Localisation of archaeological
excavations and geophysical prospections at
the Staré zámky hillfort. The polygons of the
excavation grid are based on the site reports
(Staňa, 1996, Figure 4) and (Kalčík, 2015).
Spatial localization of the excavated areas is
based on an orthophoto map from the mid-
20
th
century (ČÚZK).
0 400 m
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4. New insights about the fortifcation system
of the hillfort
The preserved remains of the hillfort’s fortifcations are
only fragmentary. The fortifcations that were located in
agricultural areas no longer exist. They have been ploughed
over and levelled with the surroundings. Their existence
is known to us based only on the fndings of earlier
archaeological excavations. However, their exact location in
the feld is problematic. The ramparts and ditches that were
located in the forested part of the site have also been only
partially preserved. The acropolis fortifcations are visible as
low terrain waves only in the northern and eastern parts of
the promontory. Over the rest of the acropolis, the rampart
of the promontory has been completely eroded. The rampart
that separated the acropolis from Bailey I, and the wall
between the frst and second bailey, have also been levelled.
The only well-preserved fortifcation at the present time is
the wall protecting Bailey II from the northwest; however,
this no longer exists outside of the forest.
The aim of the geophysical surveys was to extend our
existing knowledge of the site’s fortifcation system. We
focused on addressing issues related to the exact location of
fortifcations, as well as on the survey of the internal structure
and state of preservation of the existing parts of walls.
4.1 Acropolis
The oldest fortifcation on the site was made as early as
the Eneolithic period. From this period, we know about an
enclosing ditch, which was partially excavated (Medunová-
Benešová, 1964). It was also recorded in a magnetic survey
(Figures 3 and 4). At a length of about 65 m, it passes through
the central part of the acropolis in a north-south direction.
In three places it is interrupted by later interventions. One
of these could be an entrance. The ditch is missing in the
geophysical data on the edges of the promontory as it has
apparently deteriorated naturally. Hallstatt fortifcations had
been placed in the narrowest part of the promontory (Poulík,
1948–50, p.101), but geophysical research did not take place
there.
The question of the existence of a medieval fortifcation
older than the rampart from the 9
th
century is a problematic
one. It is often connected with a palisade recorded on the
edge of the acropolis, but its dating before the 9
th
century is
questionable (Procházka, 2009, pp.155–157). Geophysical
research in this regard did not have the opportunity to bring
new information.
From the previous excavations, we are best informed about
the perimeter fortifcations of the acropolis dating back to the
9
th
century (Figure 2). On the artifcial terrace on the slope,
foundations of a stone wall approximately 1 metre wide were
found. A substantial part of it has collapsed down the slope.
Log chambers flled with clay were adjoined from the inner
side of the rampart. A ramp made of piled up clay was also
connected to the structure from its inner side. Approximately
at the beginning of the 10
th
century, the foundation of a dry-
laid stone wall, which forms a part of the younger wall, was
embedded in the destroyed fortifcations (Procházka, 2009,
pp.152 and 155, Figure 95).
The magnetic survey was only carried out in the open
area, yet it managed to detect a part of the perimeter wall. It
showed in the data as a linear anomaly with high magnetic
values. Marginally, it can be observed at the eastern
edge of the surveyed area. Most of it was captured at the
southwestern edge of the acropolis (Figures 3 and 4). High
magnetic values (–40/+100 nT) gathered within the area of
the rampart indicate traces of high heat. This is fully in line
with the fndings of the excavation, which showed that at the
Figure 2.
Western profle of a rampart cut in the north-eastern part of the acropolis, 1 – remains of the frontal stone wall, 2 – rampart body with a box
construction, 3 – clay embankment, 4 – younger stone wall, 5 – remnants of charred wood (Procházka, 2009, Figure 95).
0 3 m
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Figure 3.
Acropolis. Magnetogram of the
surveyed area.
Figure 4.
Acropolis. Archaeological
interpretation of the magnetic prospection
data.
0 100 m
0 200 m
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turn of the 10
th
century the perimeter wall of the acropolis
was hit by a large fre and in some places, it was completely
destroyed. This is evidenced by burnt wooden crates as well
as a layer of burnt clay up to 1 metre thick (Procházka, 2009,
p.155; Staňa, 1972, p.154; 2000, p.201). On the southwestern
edge of the acropolis (in the area where the burnt-down wall
was best recorded by magnetic research), an excavation in
1965 captured a layer of burnt-earth which was part of the
destroyed wall just below the topsoil (Procházka, 2009,
p.155). The geophysical survey managed to determine the
Figure 5.
Results of GPR and ERT wall measurements on the acropolis. Above: GPR vertical time / depth section (500 MHz centre frequency antenna).
Middle: interpretation plan of GPR measurement results. Bottom: the resulting model showing the real distribution of the specifc electrical resistivity on
the measured profle, obtained by the ERT method (Schlumberger confguration). 1. preserved body of the rampart, 2. destructive layer from the outer side
of the rampart.
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189
course of the fortifcation in the part where no surface traces
were preserved. We also found that the fre we knew from
the excavation was not local, but that it destroyed at least the
entire southwest and probably the southern and eastern parts
of the wall as well.
The GPR prospection and the ERT’s main task was to
ascertain the state of preservation of the acropolis (Figure 5).
The GPR survey was able to capture homogeneous layers
that can be interpreted as remains of the body of the wall. The
anomaly with higher electrical resistivity values measured
with ERT represents the remnants of the original stone-rich
fortifcation. At the same time, it is possible to observe the
destruction layer that has spread down the slope. Therefore,
the ERT and GPR prospections fully correspond with the
results obtained from the excavation.
The ditch intersecting the acropolis in its north-western
part is dated back to the frst half of the 10
th
century (Figures
3 and 4). It separated the upper north-western part of the
acropolis from its lower south-eastern part. This ditch has
been almost completely archaeologically excavated (Kalčík,
2013, p.228; 2015, pp.138–144; Staňa, 1972, p.111). It was
also recorded in the magnetic survey. The ditch was found
to continue southwest to the edge of the acropolis. During
the excavation, the remains of the wall (in the form of its
Figure 6.
Bailey I and II. Magnetogram of surveyed area.