The Vatican City history is often conflated with that of Rome and the Roman Empire. Of course, you can’t separate the history of the Vatican from the history of Rome. Vatican City is now home to the Holy See of the Catholic Church. However, the Vatican site has been important since antiquity. But when was the Vatican built? The origins and significance of Vatican City reveal how it developed into the spiritual and administrative center of the Roman Catholic Church.
Before 27 BCE
Vaticum exists as an Etruscan–Roman area outside Rome.
1st century CE
Caligula builds the Circus Vaticanus; Saint Peter is martyred and buried nearby.
4th century (c. 326 CE)
Constantine builds Old St. Peter’s Basilica.
5th–15th centuries
Popes gradually settle on Vatican Hill; papal power expands.
1506–1626
New St. Peter’s Basilica was constructed during the Renaissance.
1870
The Papal States fell after Italian unification.
1929
The Lateran Treaty establishes Vatican City as an independent state.
Today
The Vatican remains the spiritual, cultural and administrative center of the Catholic Church.
Origins of the Vatican Area
For historians, the Vatican was once an Etruscan city called Vaticum. The Vatican Plain was never within the city of Rome. The Vatican Hill was a holiday resort for Roman nobles, who built palaces and luxury homes near the Imperial Gardens established under Caligula. Agrippina the Elder, the mother of Caligula and grandmother of Nero, also built several villas. Caligula (12-41), during his short reign (37-41), built the Circus Vaticanus, which included the obelisk now in the centre of Saint Peter's Square.
By the end of the Roman Republic (509 BCE-27 BCE), the Vatican was a small plain along the banks of the Tiber, with a small hill, Vatican Hill.
The Vatican Hill is between the Janiculum, one of Rome’s seven main hills and Monte Mario. The name Vaticanus traces its etymology back to the word “vaticinium”, which means “oracle” since many soothsayers used to occupy the place during the Roman Classical Antiquity.
Under the reign of Nero (37-68), many Christian martyrs were persecuted at the Circus Maximus. Saint Peter himself was buried there in a necropolis, where Constantine (272-337) would build the first basilica on the ruins of the Roman circus 300 years later.
Construction of Old St. Peter's Basilica
Commissioned in the 4th century, after Christianity was legalized, the ancient Basilica of St. Peter was built on the site where, according to Christian tradition, St. Peter, one of the twelve apostles of Jesus and a key figure in the early Church, was buried.
Around 319 AD, when construction began on Old St. Peter's Basilica, Constantine's workers excavated about 1 million tons of earth to prepare its foundations and worked for the next 40 years. The grand basilica stood for over 1,100 years.
The basilica undoubtedly became one of the most important pilgrimage destinations in early Christianity and established the architectural model for Christian churches, due to its characteristic wide nave, colonnaded aisles and open atrium.
In fact, its construction helped consolidate Vatican Hill as the spiritual heart of the Christian world, strengthening its role as a central destination for worship and the early Christian Church's growing authority.
Over time, the church became an important religious and ceremonial center, closely linked to the authority of the bishops of Rome. Are you ready to find out more about the Vatican City guide for tourists?
Development of the Papal Residences
After the fall of the Roman Empire in 476, the hill became the residence for the popes. Pope Symmachus built a palace at the end of the 5th century where political and religious leaders could stay, marking one of the earliest papal presences in the Vatican area.
However, for several centuries, the official papal residence remained the Lateran Palace in Rome. Due to the passage of time and political instability, various security conflicts made the Lateran increasingly unsafe. As a result, the popes began to prefer Vatican Hill, which offered greater protection and proximity to St. Peter's tomb.
During the Middle Ages, particularly under Constantine and the Lombard Kingdom, the popes received numerous donations, thereby becoming among the largest landholders in Europe. This legitimised the papal political power, and so the Vatican gradually became the administrative center of the Church.
In the 15th century, especially after the Papacy of Avignon left the Lateran Palace severely damaged, the Vatican Palaces became the permanent papal residence, a role they completed during the Italian Renaissance.
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Construction of the New St. Peter's Basilica
At the beginning of the 16th century, the ancient Basilica of St. Peter, originally built by Emperor Constantine in the 4th century, was in serious disrepair. Because of this, Pope Julius II ordered its reconstruction in 1506. In fact, this became one of the largest architectural projects in Europe at that time.
Several of the greatest artists and architects of the Renaissance participated in the reconstruction, including Bramante, Michelangelo and Bernini. The reconstruction lasted more than a century and was finally completed in 1626.
Due to its large scale, its dome and its decorated interior, the new St. Peter's Basilica became the spiritual and architectural center of the Catholic world.
At the same time, the reconstruction of the basilica formed part of a broader transformation of Rome into a center of Renaissance culture. Under the rule of Pope Julius II, Michelangelo painted the ceiling of the Sistine Chapel, the Vatican Gardens were redesigned, and the Cortile del Belvedere was constructed, reshaping the Vatican's urban and artistic landscape.
Some of the masterpieces acquired during the period were the Laocoön and His Sons and the Apollo Belvedere, which were later displayed in the Vatican City Museums and galleries. The popes were the first to make their art collections public.
Establishment of Vatican City as an Independent State
Following the French Revolution, Napoleon’s troops entered Rome on 6th February 1798, forcing the pope into exile and placing the Papal States under foreign control. He was forced to leave Rome and the Papal States fell under the control of the Directory. Although the territories were briefly restored after the Congress of Vienna in 1815, papal political power continued to decline throughout the 19th century.
During the Italian unification movement, large parts of the papal territory were annexed. In 1870, the Italian army conquered Rome, bringing an end to the Papal States. Pope Pius IX refused to recognize the new Kingdom of Italy, leading to the prolonged conflict known as the Roman Question.
When the Italian army conquered Rome in 1870, the pope suddenly lost all his political territory. Instead of leaving, Pope Pius IX decided to remain inside the Vatican, calling himself “The Prisoner of the Vatican.” Although he remained behind its walls, the Italian government allowed him to continue his religious functions as head of the Catholic Church. Although Italy passed the Law of Guarantees in 1871 to protect the pope's independence and rights, tensions between the Vatican and the Italian state persisted until 1929.
So, when was the Vatican established? Well, this dispute was finally resolved in 1929 by the Lateran Treaty, signed between the Holy See and the Italian government. This established that Vatican City is an independent sovereign state. In addition, it also recognized the temporal authority of the Pope and defined his status as an elective absolute monarch.
Modern Developments in Vatican City
Today, Vatican City has had to adapt to a changing world and societies, but it has also invested its efforts in carefully preserving its deep historical, cultural and spiritual identity.
Although its territory covers less than half a square kilometer, the Vatican continues to have major global influence due to its enormous diplomatic network, its role in international mediation and dialogue, and its status as the spiritual center of the Roman Catholic Church.
The Vatican modernized its administrative and cultural institutions, introducing new technologies and initiatives that demonstrate its commitment to environmental responsibility and sustainability. For example, the Holy See has installed large-scale solar facilities.
In addition, the Vatican continues to expand its scientific and historical research. Ongoing archaeological excavations beneath St. Peter's Basilica have revealed new evidence of ancient Roman infrastructure and early Christian cemeteries.
At the end of the Holy Year, on January 6, 2026, an estimated 33 million people will have participated in the Vatican celebrations. This means that there will be more than 90,000 visitors every day. Generally, the busiest period is the Youth Jubilee (July 21 to August 10), as it attracts more than 13 million pilgrims to Rome in just three weeks.
Today, Vatican City functions as a sovereign state and cultural institution, and is one of the world's most important tourist sites. Each year, millions of visitors pass through its gates to attend papal audiences, participate in religious ceremonies, or explore its unparalleled artistic and architectural heritage, which includes the Vatican Museums, the Sistine Chapel and St. Peter's Basilica.
Find out more about what to see at the Vatican, such as the Sistine Chapel and Saint Peter's Basilica, and fall in love with its history.
References
- Saint Peter’s Basilica | History | Research Starters | EBSCO Research. (n.d.). EBSCO. https://www.ebsco.com/research-starters/history/saint-peters-basilica
- Owen Chadwick. (1998, April). The Prisoner of the Vatican. Oxford Scholarship Online. https://academic.oup.com/book/26645/chapter-abstract/195382782?redirectedFrom=fulltext
- Vatican sees record number of visitors during Jubilee year, officials say. (2026, January 5). The Catholic Register. https://www.catholicregister.org/item/3269-vatican-sees-record-number-of-visitors-during-jubilee-year-officials-say
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