Centuriation

Centuriation, also known as the Roman grid, was a special way the Romans measured and divided land. They made neat, square patterns across big areas. These patterns often showed up as straight roads, canals, and farms.

Sometimes, these farms were given to Roman army veterans when they left the army. Other times, the land went back to the people who lived there before, like in a place called Orange in France.

Learning about centuriation helps us understand how places looked and worked long ago in areas once ruled by the Roman Empire. It shows us how people organized the land many centuries ago.

History

The Romans started using a special way to measure and divide land, called centuriation, around the fourth century BCE. They first used it when they set up new towns near Rome. Later, they used this method in places like the Po valley, starting with a town called Ariminum (now Rimini) in 268 BCE.

An important law by Tiberius Gracchus in 133 BCE helped this land division grow. Centuriation was used to give land to soldiers after battles and to use unused land better. It was used all over Italy and in some other places ruled by Rome. For example, between Rome and Salerno, people found many ways the Romans divided their land.

System and procedure

The Romans had a special way to divide land called the ager centuriatus system. A surveyor would start by finding a central point, called the umbilicus. He would face west and name the areas around him: ultra for the land in front, citra for the land behind, dextera for the land to his right, and sinistra for the land to his left.

He would then use a tool called a groma to draw two main roads crossing each other. The east-west road was called the decumanus maximus, and the north-south road was called the cardo maximus. These roads helped make a grid pattern to organize the land.

Measurement instruments

The Romans used special tools to measure land. One tool was called a Groma. It helped them see straight lines from far away. They also used a Chorobates to check if the ground was level. And they used a Dioptra to measure angles and slopes. These tools were important for their land surveys.

Orientation

Some think the Roman way of dividing land may have inspired Thomas Jefferson when he suggested making a grid of townships for the United States Public Land Survey System. You can still see similarities between the two systems in places like Italy.

But unlike the U.S. system, not all Roman land divisions followed the exact north, south, east, and west directions. Sometimes, the shape of the land or the hills and valleys decided the direction. Other times, it followed old roads or other natural features of the land. Even though it usually happened on flat land, these divisions were also found in hilly areas.

Centuriation of the surrounding territory

The central point of the land survey, called the umbilicus agri, was sometimes found inside a city or a military camp castrum. This point was known as the groma, named after the tool used by surveyors gromatici.

From this center, the main north-south road (cardo maximus) and the main east-west road (decumanus maximus) were extended beyond the city gates into the nearby farmland. Additional roads called limites quintarii were built every 100 actus (about 3.5 km) along these main roads, creating a grid pattern.

The land was split into square sections called centuriae. Later, these squares were further divided into smaller parts, each called a heredium, which were about half a hectare in size. Each heredium could be split again into two plots of land called jugera, measuring about 2,523 square meters.

Regions where centuriation was used

You can still see the effects of ancient Roman land planning in parts of Italy today. Straight roads, canals, and property lines laid out by the Romans are still part of the landscape.

• Cesena, and the areas north-east and north-west of the city;
• Central Romagna;
• Padua, eastern part of the area; in this part of Venetia, the layout is called the Graticolato Romano;
• Ager Campanus (Acerra, Capua, Nola, Atella);
• Florence (Florentia), from the first century CE, in the plain west of Prato and beyond.
• Province of Bergamo: You can still see clear traces, from the low plain up to the hills, like the straight road about ten kilometres between Spirano and Stezzano, passing through Comun Nuovo; there are also signs of old farming layouts in the streets of Treviglio.

• Béziers
• Valence
• Orange (Orange B)

Traces of centuriation in Hispania

• Tarragona
• Empúries
• Girona
• Barcelona
• Cerdanya
• Isona (Pallars Jussà)
• Guissona
• Lleida
• els Prats de Rei (old Roman Segarra)
• la Seu d'Urgell or Castellciutat (likely)
• Bages (likely)
• Castell-rosselló (likely)
• Sagunt (Saguntum)

Traces of centuriation in Britannia (present-day southern and central Britain)

• Ripe, Sussex (likely)
• Great Wymondley, Hertfordshire (Roman field system found, maybe part of a map)
• Worthing, Sussex (likely)

Traces of centuriation in Dacia (present-day south-western Romania)

• Sarmisegetuza (including areas Micia and Aquae)
• Apulum (likely)