Corinth Computer Project: Roman Grid Plan

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Greek City, pre-146 BC | Roman History | 146 - 44 BC | 44 BC | AD 70s | Roman Forum, AD 150 | Grid Plan

Roman Grid Plan, 44 B.C.

The study of the overall framework of the Roman city of Corinth is best begun by means of an examination of the Roman roads known as a result of archaeological excavation. There are currently seventeen such known Roman roads. Although general plans and state drawings exist for many of these roads, no overall study or detailed evaluation has been made of all of them until now. These roads have been excavated at different times and under varying circumstances. The best known of these Roman roads and the most easily visualized in the modern day is the Lechaion Road that has been excavated for a stretch of over 85 meters from the area of the Roman forum towards the north. There are other, shorter segments of Roman roads that are less well known and fairly obscure to locate and survey. Many of these roadways are known in the area of the Roman forum and some of the Roman roads clearly have Greek predecessors. Most of the limestone-paved roadways of Roman Corinth are datable to the period following the earthquake of 77 A.D. Many of the same roads will have had early Roman predecessors. Using the surveyed evidence of the seventeen excavated Roman roads as a framework, both for the purpose of location as well as the orientation of roadways, supplementary data has been added to the map. The so called "shadow lines" that are visible from the aerial photographic survey of the early 1960's have provided valuable clues about the size and organization of the Roman city.

Many of the dozens of discovered "shadow lines" have corresponded with the orientation of the archaeologically attested Roman roads, and others with the modern village roadways (some of which are likely vestiges of the Roman roadways) and some with both. Still other "shadow lines" suggest Roman roadways that are otherwise unattested as a result of excavation and survey and have little relation to aspects of the modern village.

Of course, one of the difficulties of using "shadow line" evidence, or evidence from the association of modern roadways with ancient thoroughfares is the problem of chronology. It is sometimes difficult to know, for example, with which chronological phase of the Greek or Roman city to associate roads known only as "shadows" in the ground. These "shadow lines" are illustrated in the aerial imagery section of this website. The aerial photograph depicts the eastern region of the town and the amphitheater. There are several shadow lines that can be seen, often as straight white lines across darker modern fields. One is clearly an extension of the modern east-west village road at the bottom center of the photograph.

Figure 1 is a composite drawing illustrating the combination of multiple sources of evidence that bears on the organization and location of the colonial Roman roadways. The information comes from excavated roadways, "shadow line" evidence, modern field boundaries and modern village roadways, modern building and lot lines and topographical features. When the roadways known from these combined sources of evidence are extended, the outlines of the grid of the plan of the Roman colony can be seen. This evidence from topographical maps, air photographs and surveyed monuments and roadways suggests that the colonial city as surveyed by the Roman architects and engineers extended from the amphitheater on the northeast to the modern village of Anaploga on the southwest, a total east-west distance of 2266 meters or 7680 Roman feet. Figure 2. The total distance north-south, from the lower slopes of Akrocorinth, on the south, below (to the north of) the Demeter Sanctuary, to the area immediately south of the gymnasium and the Sanctuary of Asklepius on the north is 1062 meters or 3600 Roman feet.

The principal axis of the colony as well as the primary north-south thoroughfare of the city is the cardo maximus, which is the Lechaion Road, dividing the urban area into two nearly equal east- west segments. From "shadow line" evidence it is clear that the principal thoroughfare continues on the same axis to the north of the urban colony and continues in the plain towards the Roman Lechaeum harbor as described by Pausanias (2.3.2). From the evidence of the air photographs and the "shadow lines" found therein, the roadway can be clearly traced at least as far as ca. 2600 m to the north of the rostra.

There are a number of major east-west decumani identified within the colony. These are major thoroughfares that are known either as the result of excavation or are prominent in the "shadow line" evidence of the air photographs (Figure 3). One is the east- west road south of South Stoa and Temple E, that has been designated decumanus by the excavator (Figure 4). Another is the east-west theater road. A third major decumanus is the roadway that is prominent in the far eastern region of the colony, seen as a "shadow line" in (Figure 1) leading toward the east and a Greek gate. In the northwest area of the colony there is a prominent east-west road that leads towards the Greek Sicyonian Gate near the northwest corner of the Greek and the Roman city. It is important to include a note of caution here since we obviously know the most from archaeological evidence as well as "shadow line" evidence about the Roman colony as fully developed, from a later chronological phase of the city. Therefore some, but not necessarily all, of these major east-west decumani may have been equally important as a part of the original colonial plan. The actual topographical center of the urban colony (Figures 2, 3) is in the area of the rostra in the forum. Although the east- west orientation of the rostra is not according to that of the colony but rather that of the nearby Hellenistic South Stoa, the length of the rostra falls generally within the north-south corridor of the cardo maximus (discussion below).

Figure 1: Evidence for roadways in the Caesarean colony of 44 B.C. from all available sources.

Click on the plans to enlarge.

Figure 2: Schematic drawing of the four quadrants of the urban colony, each of which is 32 x 15 actus, with centrally located forum and cardo maximus.

Figure 3: "Drawing board" plan of the
urban colony of 44 B.C.

Figure 4: Detail of the area of Forum Southwest, cardo II west to cardo III west, and the decumanus, illustrating the points at which the surveyed measurement was taken.

Altogether the combined evidence suggests a colonial plan, the overall area of which was based on four equal quadrants or centuries, each 32 X 15 actus or 240 iugera. There exist a total of 29 cardines and 29 one actus wide insulae, in each of the four centuries, as the colonial city planner designed it, although there may have been some modifications between design and use. The westernmost insula of the eastern two centuries included the cardo maximus, the principal north-south artery, which had reserved a width of 50 feet (including the sidewalk). The average width of the remaining cardines appears to be ca. 12 feet. There were likely six decumani in both the southern and northern half of the colony for a total of 12, resulting in an average width of 20 feet each.

As is common in Roman colonies and cities, a political, social and economic 'center of town' was reserved from the earliest planning of the colony, and this seems to have been the case at Corinth. The central public area that would have included the forum as its major component appears to have been originally designed for an area of 24 square actus or 12 iugera; 6 city insulae east-west and 4 city insulae north-south. This entire area comprised the topographical center of the colony, with the location of the rostra as the central feature of both. This arrangement would have meant that equal space, 6 square actus or 3 iugera, would have been utilized from each of the four intersecting centuries for the composition of the forum (Figures 2, 3). Neither the cardo maximus nor a major decumanus of the city actually intersected at the rostra but the axes of these roadways, from the point of view of the original city planner, certainly did. There were, of course, other public areas near the center of the colony that would also have been used by the citizens, for instance the theater to the northwest, but it would likely have been a separate area from the standpoint of Roman colonial planning. The actual area of the forum was planned to be a relatively small proportion of the urban area of the colony; 12 iugera out of a total area of 812 iugera or 1.48 %. It is also clear that from the earliest Roman colonial plan, a number of Greek structures were located within the area reserved for the Roman forum, principally the Hellenistic South Stoa.

Although there may have been some variation in the number of decumani of the urban area from century to century, each of the resulting four centuria strigata (29 X 14 actus), which was the land exclusive of the roadways, and additionally the land excluded by the forum, would likely have been originally planned for 200 iugera.

Within each of the four large centuries of the colonial city can be reconstructed insulae based on the available evidence. The insulae are one actus wide , east-west, and from the combined information of archaeological evidence, air photographs and modern lot lines and in some cases topographical features, appear to vary in north-south length between one and four actus (120 and 480 feet). There is growing evidence for what the 44 B.C. colonial plan may have been; It is clear that it was a per strigas plan for the colony, and likely to have been a combination of 1 X 1, 1 X 2, 1 X 3 and 1 X 4 actus insulae. Because of topographical considerations, as well as considerations of earlier existing monuments, there would have been variations in colonial design that are reflected in this layout. These insulae are divided by roads, both east-west decumani and north-south cardines. Some of these one actus squares are still visible in modern lot and house lines and still can be found in several parts of the modern village of Ancient Corinth as well as in nearby Anaploga. There were, in addition to the Roman insulae and roadways, earlier Greek roadways that were likely respected by the Roman colony.

The best source of information about the measurement of the insulae as one actus wide, as well as information about the specific length of the foot measure employed in the Roman planning of the colony, comes from a block that has been measured in the area of the southwest forum, between cardo II west and cardo III west (Figure 4). Between the exterior faces of the walls of the existing buildings the surveyed measurement is 35.486 meters which gives 120 feet of 0.295 + m. The fact that the sidewalks as well as the roadways would not have been included in the 120 foot wide insulae suggests that the Roman legal term iter populo non debetur, "the public thoroughfare is not indebted" was the system of land division employed in the urban Roman colony. This would have meant that the roads were not included within the measured 120 foot wide insulae, but were constructed outside of the insula blocks.

As a result of this field survey we know the north/south orientation of the east curb of the cardo maximus (and the colony) to be N03d 3' 46"W and the orientation of the south curb of the major decumanus, south of the South Stoa, to be N86d 56' 09"E, a difference of only 5 seconds of one minute of one degree from being an exact ninety degree difference.

An obvious planning consideration of the Roman architects and engineers was that the Roman colony of Corinth in its limits, fit well within the Greek city walls of the former Greek city to the east, south and west. Only on the north is there a relatively small portion of the northwest century of the urban colony that does not fall within the Greek city circuit wall. On the other hand, to the north of the northeast quadrant of the colony, and technically outside of its limits, is a wide and fertile plateau that lies well within the Greek city circuit wall and which logically would have been utilized for agricultural purposes by the colonists. It appears from the evidence of the field lines and the 'shadow lines' that on this portion of the land an earlier scheme of land division may have been retained.

The east-west northern limit of the urban colony comes very close to the line of the Late Roman wall, found to the west of the Gymnasium and southwest of the Asklepieion. The east-west southern limit of the colony is found close to the location of the Hadji Mustafa fountain, a spring likely to have been used in both Greek and Roman times. The location of the fountain is included within the Roman colonial plan. There is a rapid rise in the lower slope of Acrocorinth immediately to the south of the fountain house and the scarp, or a portion of it, may well have been the southern line of the colony. The eastern north-south limit of the colony falls just to the east of the later built amphitheater. The western north-south limit of the colony is close to the western edge of Anaploga.

It is clear from the nature of the plan of the Roman colony that from the beginning a number of the Greek city gates were used by the Romans. The evidence for this use is the extension of many of the major thoroughfares of the Roman colony, east-west as well as north-south, known from the archaeological evidence of the roadways and from air photographs, beyond the limit of the colony to or toward the Greek gates (Figure 4). There are also a number of irregularities of the Roman plan that may have to do with the previously existing Greek roadways and Greek gates. Although the overall system of the Roman colony was surveyed and set out according to a "new" orientation, it appears that the Romans did employ some aspects of the previously existing Greek orientations in their planning strategy. The axis of the open area of the forum proper, north of the South Stoa, was laid out at an orientation that was not in keeping with the grid of the Roman colony but rather in keeping with the orientation of certain Greek structures and roadways in the center of the Greek city as well as certain "Greek" land division lines to the north of the Roman colony. Later in the history of the Roman colony a number of important Roman buildings were built according to the same axis, the Julian Basilica, Temple E and the Temple E precinct as well as some of the small temples at the west end of the forum.

What have we learned about the actual work of the Roman agrimensor, his assistants, the finitores, and their method of laying out the colony? The Roman surveyor with his principal surveying instrument, the groma, would in the earliest stage of surveying, have set up his instrument high on the southern slope of Acrocorinth, likely above what would become the southern limit of the urban colony. The groma, which was a vertical staff with a cross mounted on a bracket, included two horizontal arms, each with two paired plumb lines and plummets. Sighting was accomplished by lining up one plumb line with its opposite number. Although a relatively simple process, the equipment was extremely accurate in the surveying of straight lines and right angles, meaning squares and rectangles. The groma would have been utilized in conjunction with one, or likely more, metae (sighting rods). From the high vantage point on the north slope of Acrocorinth to the south of what would become the forum, the surveyor could have sighted virtually the entire length of the principle north-south axis of the colony, the cardo maximus, both that within the urban area of the colony as well as the area to the north, between the Greek Long Walls, as far as 5000 m. away toward the Corinthian Gulf. From the location on the north slope of Acrocorinth it is also likely that he could have sighted the rostra, the topographical center of the urban colony and the center of the forum.

After the principal north-south line of the colony had been determined, the groma would have been moved along the Cardo Maximus to measured locations where the decumani would have been sighted, surveyed and laid out. Crosschecks would have been made during this process. This survey procedure, as the principal means of measurement and division of property, would have continued for the entire length of the cardo maximus and then extended to the breadth of the centuriated area, although the details of land division would have differed to some degree in the land reserved for agricultural use (discussion below). Boundary stones, termini, would have been set up around the fines of the territorium. Following the survey it would have been likely that the forma, the plan of the urban colony including the adjoining land, the territorium, would have been set up in the forum.