In antiquity, a civil basilica was a grand public building with a semi-sacred significance, serving a variety of purposes. These structures were commonly used for court hearings, public assemblies, and, at times, for commercial activities such as shops and financial transactions.
The architectural style of the basilica, known for its expansive covered space, originated in Ancient Greek architecture and was later adopted and enhanced in Roman architecture, becoming a distinctive feature of Roman cities.
Unlike Christian basilicas, ancient basilicas did not serve religious functions.
See main article: article and Stoa.
The word "basilica" derived from the Latin term basilica, originates from two Greek elements: basileus, meaning "king", and the feminine adjective suffix -ikê. The full Greek expression is (basilika oikia), which translates to "royal hall". This was traditionally a place where the king or his representatives would grant public audiences, dispense justice, and serve as a venue for public assemblies.The concept is related to the Greek stoa, a public covered space designed to shelter various activities from the weather. Over time, the stoa acquired a more specialized function, such as the stoa basileios in Athens, which served as the seat of the archon-king. These structures typically had an entrance enclosed at the back by a solid wall and opened onto the public space (the agora) at the front, featuring a portico with a colonnade.
The Roman basilica, which emerged in the 2nd century BC, was inspired by and named after the Greek stoa basileios. The development of the Roman basilica followed a path similar to that of the Greek stoa. Initially designed as a public space providing shelter from the weather, the basilica evolved to serve specific functions, particularly in the administration of justice. All Roman basilicas were used for legal proceedings. For example, in Rome, the tribunes of the plebs held their hearings in the Basilica Porcia, while the Centumvirs court met in the Basilica Julia. By the early 2nd century BC, this type of building, which provided a spacious and sheltered open area, became a significant feature in Roman cities, with most courts across the Empire utilizing it.
Every well-developed Roman city had a basilica, typically situated next to the forum. Some basilicas were associated with shops (tabernae), which opened either onto the exterior (as seen with the Basilica Aemilia, or tabernae novae) or onto the interior (as seen with the Basilica Julia). These shops may have been used by bankers and pawnbrokers.
The typical floor plan of a Roman basilica is rectangular, with at least one end featuring an apse, a semi-circular or polygonal recess often used as a court or to house a statue of the Roman emperor. A basilica with an apse at each end is known as a double-apse basilica. The apses, or exedras, may be incorporated within the rectangular plan or extended outward, as seen in the Basilica Ulpia.
The interior of a basilica is divided into multiple naves by rows of single or double columns. The central nave, known as the spatium medium, is the widest and extends nearly the full length of the rectangular plan. It is flanked by side naves—one on each side for basilicas with three naves, or two on each side for those with five naves. These side naves are narrower, and sometimes lower, than the central nave but are of equal length. The interior space may be covered by either a wooden framed ceiling or a vaulted ceiling supported by pillars. The central nave is typically taller than the side naves, allowing for the installation of windows in the upper part of the walls, which provides natural light to the interior. In larger basilicas, the ground floor arcade is often complemented by a second or even a third level of colonnades that support the windowed walls. The side naves are sometimes topped with an additional story, creating a gallery that overlooks the central space.
The initial basilicas constructed in Rome during the 2nd century BC were influenced by Greek architectural models, reflecting the impact of Roman campaigns in Macedonia and Syria. The first small basilica was built on the Roman Forum, later occupied by the southern section of the Basilica Aemilia. This earliest structure, dating from the end of the 3rd century BC, is not specifically named but is referred to as a basilica by ancient authors.
Between 184 and 170 BC, the Porcia, Aemilia, and Sempronia basilicas were constructed around the Forum, each named after the censor who commissioned its construction. These basilicas were adorned with various artworks obtained from conquered territories. By the mid-5th century AD, Polemius Silvius listed eleven basilicas in Rome, highlighting the architectural and cultural significance of these structures in the city.
| Basilica Aemilia | 179 BC | Roman Forum | Marcus Aemilius Lepidus and Marcus Fulvius Nobilior | |
| Basilica Alexandrina | Around 230 AD | Campus Martius | Marcus Aurelius Severus Alexander | |
| Basilica Argentaria | 113 AD | Imperial fora | Trajan | |
| Basilica Hilariania | Around 150 AD | Caelian Hill | Poplicius Hilarus | |
| Basilica Julia | 46 BC | Roman Forum | Julius Caesar and then Augustus | |
| Basilica of Junius Bassus | 331 AD | Esquiline Hill | Junius Bassus (consul) | |
| Basilica Matidiae and Marcianae | 120 AD | Campus Martius | Hadrian | |
| Basilica of Maxentius | Around 310 AD | Velian Hill | Maxentius and then Constantine the Great | |
| Basilica of Neptune | 25 BC | Campus Martius | Marcus Vipsanius Agrippa | |
| Basilica Opimia | 121 BC | Roman Forum | Lucius Opimius | |
| Basilica Porcia | 184 BC | Roman Forum | Cato the Elder | |
| Basilica Sempronia | 170 BC | Roman Forum | Tiberius Sempronius Gracchus (consul 177 BC) | |
| Basilica Ulpia | 112 AD | Imperial fora | Trajan |
See main article: article, Basilica and Basilicas in the Catholic Church.
The floor plan of the Roman civil basilica served as a model for the construction of the first Christian churches in late Antiquity. This influence is evident in the continued use of the term "basilica" to designate certain churches from the time of Constantine onward. Today, the term "basilica" is still used for religious buildings of significant importance that, while not functioning as cathedrals, are granted special privileges.