ROMAN URBAN TOPOGRAPHY in Britain and the western Empire

Fig 16 Simplified plan of Roman York, showing how one of
the two roads from the north-west led straight to the
fortress principia, while the other bypassed the
fortress and led to the bridge joining it with the
civilian settlement
with round numbers, to obtain his correct proportions it
was frequently necessary to depart from integral, let alone
round numbers.
For sizes of urban insulae we have only modern figures,
obtained from remains, but unfortunately too often
imprecise (Castagnoli 1956). These suggest that round
numbers of Roman feet were not always achieved. At
Thamugadi (Timgad, Algeria), where many insulae are
well preserved, the figure of about 70m does correspond
roughly with 2 actus (= 240 Roman feet). But for insulae in
Italian colonies, possible round numbers in pedes monetales
of 200, 210, 270, and 280 do not suggest measurement
in actus. A theory that passus were involved in urban
planning comes from a study of distances between the
Roman bridges of Padua (Galliazzo 1971, 162). We cannot
disprove this, since either 100 and 200 passus or 500 and
1000 Roman feet are round numbers.
When we turn from general matters to study the role of
surveyors in Romano-British town planning it is necessary
to take account of (a) the different types of settlement, and
(b) comparisons with other parts of the Roman Empire,
within the perspective of the whole history of ancient town
planning (Castagnoli 1956; Chevallier 1974; Ward-
Perkins 1974; Rykwert 1976). We can perhaps classify
urban settlement thus: (i) colonies; (ii) other newlyplanned
towns, especially civitas capitals (Wacher 1966);
(iii) minor settlements (Rodwell & Rowley 1976).
The three early coloniae, Colchester, Lincoln, and
Gloucester, were all adapted from existing legionary
fortresses on exactly the same site, as were the civitas
capitals of Exeter and, probably, Wroxeter (Crummy
1982). Centuriation is unexpectedly absent, as far as we
know, round the British coloniae, though more may be
11
Dilke: Ground survey and measurement in Roman towns
discovered; north-north-west of Colchester there are
interesting traces of roads at right-angles and significant
‘street’ names (A Syme, pers comm), and Roman field
patterns, difficult to interpret, have been observed round
Gloucester (Rawes 1979).
We may compare and contrast the colonies in Britain
with a typical colony in the Po valley. At Parma (Tozzi
1974), founded in 183 BC, the Via Aemilia goes through
the town and the surrounding land was all centuriated.
The kardo maximus and decumanus maximus appear to
meet outside the ancient town centre, in an area where
there was a Bronze Age settlement. Such an intersection is
regarded as most common, even if not most perfect, in the
Corpus Agrimensorum; as a result, one needs to be careful
before speaking of the main streets of a town as the kardo
maximus and decumanus maximus. The roads leading
directly north and south from the colony corresponded to
the limites of the centuriation. In Parma itself and to the
west the decumanus maximus coincided with a long straight
stretch of the Via Aemilia, whereas to the east this road
diverged from the orientation of the centuriated land.
Nevertheless, although the Via Aemilia was planned in
187 BC and the colony four years later, it is possible that
the two were considered together as part of the same
overall plan (Tozzi 1974,47, n5; read ‘da SSO a NNE’).
By way of new towns, Britain was well supplied with
civitas capitals (Wacher 1966; 1975), often built on new
sites as part of a policy of ‘Romanization’. Such a site is
Cirencester (McWhirr 1981, 11,21; McWhirr & Wacher
1982,65-6), set up in c AD 70 for the Dobunni, who had
been at Bagendon and elsewhere. The forum lay immediately
north-west of a preceding fort, while the
amphitheatre was to the west, its entrance some 650m
west-south-west of the nearest part of the forum. When
the amphitheatre was made, evidently out of disused
quarries, the Fosse Way may have had to be slightly
rerouted. Cirencester was a road junction, and on the east
side of the town was a bypass which joined the Silchester
road with the northward continuation of the Fosse Way,
without crossing the river Churn. This provision is likely
to have been made before the foundation of the town.
Few towns remained unchanged throughout their
history, and the skill of Roman surveyors can often be seen
in the major replanning of an existing settlement to take
account of a change in circumstances. Thus when in the
early 3rd century York became a colonia and, evidently,
the capital of Britannia Inferior, it was clearly redesigned
(Fig 16). The place had a strong military function and so
the town planners conceived it as a double city divided by
the Ouse, the left bank containing the base for Legio VI
and docks along the river Foss, the right bank the imperial
palace and the civilian settlement. From the point of view
of planning an interesting feature is that between the
legionary fortress and the river there was a road, so that
civilians had no need to enter the military area. The line of
this useful bypass was not exactly parallel to the wall of the
fortress. It has also been noted (Wacher 1975, 156) that
the baths and other buildings of the imperial palace were
on a slightly different alignment from the civilian settlement.
For different functions on opposite sides of a river
we may compare a Greek city, Megalopolis (Dilke & Dilke
1973).
As an example of adaptation and replanning, the layout
of Silchester (Boon 1974; Wacher 1975, 255-77) differs