The Roman Underworld: Catacombs, the Cloaca Maxima and hidden routes

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Tunnels and Passages: The Hidden Routes of Roman Engineering.

The Roman underworld include various underground structures such as catacombs, underground passages, and sewers, notably the Cloaca Maxima. These subterranean elements served multiple functions ranging from burial practices and religious activities to waste management and public sanitation. Originating as early as the founding of Rome, these underground constructs evolved over time to meet the demands of a growing and complex urban population. Their historical significance is evident not just in the context of Roman civil engineering and architecture, but also in the ways they influenced religious, cultural, and even economic activities.

Featured image: The Catacombs of St. Domitilla not only rank as the most extensive, but they are also the best preserved among all catacombs. Uniquely, they feature a subterranean Basilica of St Nereus and St Achilleus, dating back to the 4th century.

Related articles: Apartment Living in Ancient Rome: Insulae Life and Culture

Historical Background

Early Foundations of Subterranean Rome

The early history of subterranean Rome can be traced back to the very foundations of the city itself. Rome, originally built on the banks of the River Tiber, faced several challenges that made underground construction not just viable but also necessary. The topography of the Seven Hills of Rome provided both opportunities and challenges for urban planning. As a result, subterranean structures such as tunnels, sewers, and catacombs were established over time to address various logistical and practical concerns.

Some of the earliest examples include simple drainage ditches and tunnels aimed at preventing flooding, as well as underground storage rooms (cellars) for keeping perishable goods cool. The techniques employed in these constructions were heavily influenced by earlier civilizations, such as the Etruscans, known for their expertise in hydraulic engineering. Over time, these foundational elements would evolve into far more complex systems like the Cloaca Maxima, one of the world’s earliest sewage systems, and the intricate catacombs that extend for miles beneath the city.

Sociopolitical Factors Contributing to the Construction of Underground Structures

Sociopolitical factors played a significant role in shaping Rome’s subterranean landscape. One of the principal drivers was the concept of “Romanitas,” the cultural and political identity of being Roman. Public works were considered a representation of the state’s power and served to distinguish Roman civilization as organized and advanced. As such, large-scale infrastructure projects, including subterranean ones, were often funded by the state or wealthy patrons to reflect this cultural ethos.

Furthermore, religious beliefs and practices also had an impact. The construction of catacombs, for instance, was deeply intertwined with Roman laws on burials within city limits and the growth of Christianity. These underground burial sites provided a solution to land scarcity and allowed for practices that were religiously and culturally significant.

The Roman military and governance also influenced underground construction. Tunnels and passageways were often used for strategic purposes, such as quick and covert transportation of troops or goods. The development of these structures was therefore not merely a matter of engineering ingenuity but also a product of military necessity.

Another factor was the issue of public health and sanitation. With a population that could exceed one million people, Rome faced significant challenges related to waste management. The sewer systems were thus not just feats of engineering but were crucial in controlling the spread of diseases and improving public health.


Related articles: The Capuchin Catacombs of Palermo

Origins and Construction

The catacombs in Rome can be traced back to the 2nd century AD, although some might have earlier origins. Initially, these subterranean burial chambers were built by Roman Jews and later extensively used by Christians. Catacombs were often constructed on the outskirts of Rome due to Roman laws that prohibited burials within the city walls.

While catacombs are most renowned for Christian burials, they were not exclusive to this religious group. Starting in the 2nd century AD, catacombs became burial sites for Jews and followers of various pagan Roman religions. Two primary reasons drove this burial practice: the ancient Roman prohibition on interments within city limits and challenges such as land scarcity and overcrowding. Rome houses multiple catacomb sites, both Christian and non-Christian. Some of these historical burial places have been overtaken by contemporary urban development.

Christian catacombs hold immense significance in understanding Early Christian art. They preserve a vast collection of pre-400 AD artworks, including frescoes, sculptures, and gold glass medallions. It should be noted that while these artifacts remain, many of the bodies have been relocated. Similarly, the Jewish catacombs provide invaluable insights into Jewish culture during this ancient era.

Materials Used

The primary materials used in the construction of catacombs were tufa and pumice, types of volcanic rock that were abundant in the Roman countryside. These rocks were relatively easy to carve but also stable enough to support underground structures.

Engineering Techniques

Excavators, known as fossors, engineered intricate networks of corridors and tunnels, layering them atop one another. These catacombs extend 7–19 metres (23–62 ft) beneath the ground, spanning an expanse greater than 2.4 square kilometres (590 acres). Connecting these layers are slender staircases that can span up to four levels deep. The typical dimensions of these corridors are approximately 2.5 by 1 metre (8.2 ft × 3.3 ft).

Uses and Functions

Burial Practices

Burial niches, known as loculi, were chiseled into the catacomb walls. These niches measure 40–60 centimetres (16–24 in) in height and 120–150 centimetres (47–59 in) in length. Deceased individuals were laid within stone chambers or sarcophagi, dressed in their attire and wrapped in linen. These chambers were then sealed with a stone slab, inscribed with the individual’s name, age, and date of passing.

Religious Activities

Beyond serving as burial sites, catacombs had a religious significance, particularly for Christians. They were often used for clandestine worship and other religious ceremonies during periods of persecution. Some catacombs contained small chambers known as cubicula, which were reserved for wealthier families and sometimes used for religious rites. In some cases, the underground chambers contained altars and other ritualistic elements that facilitated worship. Certain underground locations were considered sacred sites, often connected with a specific deity or religious belief. For example, the Mithraea, underground sanctuaries dedicated to the god Mithras, were venues for initiation rites and other ceremonies. These sites served as spaces where religious communities could gather in relative privacy to perform their practices.

Related article: The Mithraeum of san Clemente

The Crypt of the Popes, source

Famous Catacombs

Catacombs of Callixtus (Catacombe di San Callisto)

Located along the Appian Way, the Catacombs of Callixtus are among the largest and most important in Rome. They span over 12 miles and have multiple levels. This catacomb is noted for the Crypt of the Popes, which contains the tombs of several early Christian Popes. The Catacombs of Callixtus served as a vital religious and cultural landmark during the early Christian era.

Grave of Saint Cecilia
Catacombs of Priscilla (Catacombe di Priscilla)

Situated on the Via Salaria, the Catacombs of Priscilla are unique for their extensive frescoes, many of which provide valuable insights into early Christian art and iconography. Unlike other catacombs, Priscilla’s are known for the large number of female portraits, suggesting the catacombs’ strong association with early Christian women.

Catacombs of Domitilla (Catacombe di Domitilla)

The Catacombs of Domitilla are an extensive underground cemetery in Rome, Italy, situated over 16 meters below ground and extending 15 kilometers in distance. Ordered by the Domitilla family and dating back to 120 AD, they were in use from the 1st to the 5th centuries AD and were rediscovered in 1593. Unique features include an underground Basilica dedicated to Holy Martyrs Nereo and Achilleo and Saint Petronilla. The site contains more than 26,000 tombs and is notable for its early Christian frescoes. Unlike other Roman catacombs, it still holds human remains. Recent restoration has employed lasers to clarify wall images, and the site is currently maintained by the Divine Word Missionaries.

Catacombs S. Sebastiano Rome, source
Catacombs of San Sebastiano (Catacombe di San Sebastiano)

Located in Rome’s Ardeatino Quarter and extending along the ancient Via Appia Antica, the Catacombs of San Sebastiano serve as a hypogeum cemetery with unique historical and religious significance. Unlike many other Christian burial sites, this underground cemetery has remained accessible to the public over the centuries. Though the first of its original four levels has largely deteriorated, the catacombs continue to draw interest for their storied past.

Originally known in the 3rd century as “in memoria apostolorum,” the catacombs underwent a name change to “di San Sebastiano” during the Early Middle Ages. This early name referred to the temporary presence of the relics of Apostles Peter and Paul, adding an additional layer of religious importance to the site. Adding to the site’s religious and historical value are the confirmed internments of three martyrs—Sebastian, Quirinus, and Eutychius—in this cemetery along the Appian Way.


By 380, Christianity had been established as a state religion. Initially, there was a strong desire among many to be interred alongside martyrs in the catacombs. Nevertheless, as time progressed, the tradition of catacomb burial experienced a gradual decline. More individuals began choosing burial in church cemeteries instead.

Post the Edict of Milan in 313, a significant number of Roman Christians visited the catacombs, driven by the intent to retrieve relics associated with martyrs. This led to widespread pillaging of the catacombs in search of these sacred items, resulting in extensive vandalism.

By the 6th century, the primary use of catacombs shifted to hosting memorial services for martyrs. Even so, some artistic additions continued, with frescoes like that of Saint Stephen in the Catacomb of Commodilla being added as late as the 7th century. It is believed that the catacombs were also targeted during the sackings of Rome by the Ostrogoths, Vandals, and Lombards, likely in search of treasures.

By the time the 10th century arrived, the use of catacombs had diminished significantly. The sacred relics they once held were relocated to basilicas situated above ground.

Underground Passages

Types of Passages

Underground passages in Rome served a variety of purposes and can be broadly categorized into two types: escape routes and storage facilities.

Escape Routes

Escape tunnels were often constructed for strategic purposes. Many were designed to allow for the rapid evacuation of individuals from public buildings or private residences in times of siege or other emergencies. These tunnels typically led to safer locations outside the city walls or to fortified structures.

Storage Facilities

Apart from their use as escape conduits, underground passages also functioned as storage spaces. They were often used to store grain, weapons, and other valuable goods, safeguarding them from theft, spoilage, or damage. The constant temperature and humidity levels in these underground spaces made them ideal for long-term storage.

Construction Methods

Tunneling Techniques

The creation of underground passages involved intricate planning and advanced engineering. Most passages were constructed using the cut-and-cover method or by boring, depending on the soil conditions and the required dimensions of the tunnel. Workers often used basic tools such as pickaxes and shovels, although more complex machinery like cranes might have been used in larger projects. Ventilation and structural integrity were significant considerations, necessitating the inclusion of air shafts and support beams in the design.

Historical Examples

Passages under the Colosseum

The Colosseum, one of Rome’s most iconic structures, features a complex system of underground passages known as the hypogeum. Spread across 15,000 square metres, this subterranean network was used for a variety of purposes, including the housing of gladiators and animals before they entered the arena. It also contained mechanical lifts and trap doors that facilitated the staging of elaborate spectacles.

Roman Sewer Systems

Cloaca Maxima

Construction and Purpose

The Cloaca Maxima is one of the earliest and most well-known sewage systems in Rome, and arguably in the world. Originating as a simple drainage channel to combat the frequent flooding of the River Tiber, it was gradually expanded and covered, serving the dual purposes of stormwater drainage and sewage removal. Built primarily from carved tufa and later lined with bricks, it was an engineering marvel of its time, designed to handle the waste management needs of a burgeoning city.

View of the Cloaca Maxima Rome 1814, source
Historical Significance

The Cloaca Maxima is not just an engineering achievement but also holds immense historical importance as a symbol of Roman civil engineering and public sanitation. It influenced subsequent generations of urban planners and stands as an early example of organized waste management.

Other Sewer Systems

Localized Sewer Networks

Apart from the Cloaca Maxima, Rome had several smaller, localized sewer networks designed to serve specific districts or even individual buildings. These smaller channels were often connected to the Cloaca Maxima, ensuring a coordinated sewage and waste management system.

Waste Management

These additional sewer systems were critical for waste management. In a city where the population could exceed a million, efficient waste disposal was not just convenient but vital for public health. The sewers transported waste away from residential areas, public baths, and markets, depositing it into the Tiber River.

Maintenance and Operation

Workers Involved

Maintenance was essential to ensure the functionality of these expansive sewer systems. Specialized workers known as cloacinae were responsible for the upkeep of the sewer networks.

Cleaning Methods

Routine cleaning involved manual labor, where workers would remove blockages and debris. Mechanical devices, such as long-handled tools, were also employed to clean difficult-to-reach sections of the sewers. Additionally, during periods of heavy rain, the sewers were naturally flushed, aiding in their maintenance.

Impacts on Public Health

Disease Control

The Roman sewers had a significant impact on public health by reducing instances of waterborne diseases. By channeling waste away from populated areas, they helped minimize the spread of pathogens and harmful bacteria.

Sanitation Efforts

Sanitation was a primary concern for Roman urban planners, and the sewer systems were an integral part of this agenda. The elimination of waste from public and residential areas contributed to a cleaner urban environment, enhancing the quality of life in Rome.

Activities in the Roman Underworld

Commerce and Economy

Underground Markets

Though less commonly associated with commercial activity, certain underground passages and chambers were occasionally used as markets. These hidden venues often catered to specialized or prohibited goods, serving a clientele that sought discretion or exclusivity.

Storage of Goods

As mentioned earlier, the constant environmental conditions in the Roman underworld made it an ideal space for storing perishable items like food and wine, as well as valuable goods such as weapons and metalwork. This had a significant impact on Rome’s economy, as it enabled better stockpiling and distribution of resources.

Social and Cultural Aspects

Role in Mythology and Folklore

While the focus of this article is on the literal Roman underworld, it is worth noting that underground spaces often featured in Roman myths and folklore. They were commonly seen as mysterious or otherworldly locales, associated with gods of the underworld like Pluto and Proserpina. These cultural perceptions added another layer of significance to Rome’s subterranean structures.

Class Distinctions and the Underworld

The use and perception of underground spaces in Rome were also influenced by social class. While wealthy Romans could afford elaborate tombs in the catacombs, the poor were often relegated to less desirable underground locations for burial. Moreover, activities like manual labor in the sewers were generally performed by slaves or lower-class workers, underlining the class distinctions evident even in the Roman underworld.

Archaeological Discoveries

Recent Excavations

In recent decades, various archaeological expeditions have unearthed new sections of Rome’s underworld, ranging from previously unknown catacombs to complex tunnel systems. These discoveries often employ advanced technologies like ground-penetrating radar to identify sites before excavation begins.

Artefacts Unearthed

Many of the recent excavations have led to the discovery of important artefacts, including inscriptions, frescoes, and ritual objects. These items provide invaluable insights into the daily lives, religious practices, and societal structures of ancient Rome. For instance, frescoes in the newly discovered sections of the Catacombs of Priscilla have offered new perspectives on early Christian art and iconography.

Contributions to Understanding Roman History

The ongoing archaeological work in the Roman underworld has significantly contributed to the academic understanding of Roman history. The artefacts and structural remains unearthed have filled gaps in the historical record, shedding light on aspects of Roman life that were previously unclear or unknown.

Conservation and Tourism

Efforts to Preserve Underground Sites

Given their historical significance, there are numerous efforts aimed at preserving these subterranean sites. Conservationists use techniques such as controlled humidity and temperature to preserve frescoes and inscriptions. Additionally, measures like restricted access and monitored visitation help protect these fragile environments from damage.

Tourist Attractions

Many of Rome’s underground sites have become popular tourist attractions. Sites like the Catacombs of Callixtus and the underground passages of the Colosseum draw thousands of visitors each year. Guided tours often include historical context and interpretations, enriching the visitor experience.

Ethical Considerations

The surge in tourism poses ethical challenges, especially concerning the preservation of these ancient sites. Issues such as crowding, light exposure, and inadvertent damage by visitors are matters of ongoing concern. Therefore, authorities often have to strike a balance between making these sites accessible to the public and ensuring their long-term preservation.

Topics: Hidden aspects of Ancient Rome, Engineering techniques used in Roman Catacombs, History of Roman Sewer Systems, Public Health in Ancient Rome, Underground Activities in Roman Society, Types of Underground Passages in Rome, Ethical considerations in Roman archaeology, Storage facilities in Ancient Rome, Roman Mythology and the Underworld, Famous Roman Catacombs, Catacombs of Callixtus, Catacombs of Priscilla


Cloaca Maxima: An Engineering Marvel of Ancient Rome

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