History and Architecture of St. Peter's Basilica

In the aftermath of the Great Fire of Rome in $64 \, CE$, Emperor Nero initiated a severe persecution of Christians. Among those executed during this period were Saint Peter and Saint Paul. Historical records indicate that Saint Peter's execution took place within Nero’s circus ($\textit{Circus Neronis}$), located in the area of the Vatican hill. According to tradition, Saint Peter was executed on a cross, but at his own specific request, he was crucified with his head directed toward the ground. He believed he was unworthy to die in the same manner as Jesus, who died facing the sky. This site subsequently became a Christian burial ground during Ancient Roman times.

The Constantinian Basilica: Old Saint Peter’s

The site remained a burial ground until the reign of Emperor Constantine the Great, who ordered the construction of a church directly on top of the burial area. This structure is known as the first Basilica of Saint Peter’s or Old Saint Peter’s. Construction for this original basilica began between the years $318$ and $322 \, CE$ and required approximately $40$ years to complete. For the $12$ centuries, the church grew in prominence, eventually establishing itself as a primary site of pilgrimage in Rome. By the year $1450$, as documented in restorations from ancient authorities, the complex included various chapels, oratories, and sacred shrines attached to the main foundation.

The Renaissance Reconstruction and the New Basilica

In $1506$, Pope Julius II ordered the demolition of the Old Basilica to make way for a more magnificent structure. The construction of the New Basilica engaged every architect of significance between the years $1505$ and $1628$. Donato Bramante served as the first architect, and his original design utilized a Greek cross plan. This Renaissance approach was continued by Michelangelo, who also championed the Greek cross configuration. However, the architectural direction shifted during the reign of Pope Paul V ($\text{Borghese}$, r. $1605$ to $1621$). His architect, Carlo Maderno (a nephew of Fontana), altered the layout to a Latin cross plan, which became the final structural form of the building. Maderno was also responsible for the design and construction of the basilica's façade, completed around $1612$.

The Baroque Interior and the Influence of Bernini

Gian Lorenzo Bernini began his extensive work on the interior decoration of Saint Peter’s as a young man in $1626$ under the patronage of Pope Urban VIII ($\text{Barberini}$). Bernini served as the embellisher of the basilica for $50$ years and was officially appointed as the successor to Maderno in $1629$. His most notable contributions include the massive bronze Baldachin ($\text{baldacchino}$), which was created using bronze stripped from the Pantheon. Other major works by Bernini within the basilica include the Chapel of the Sacrament, the structural plan for the niches and loggias located in the piers of the dome, the Statue of Saint Longinus, and the Elaborate Tomb of Pope Alexander VII ($\text{Chigi}$). One of his crowning achievements is the Throne of Saint Peter ($\text{Cathedra Petri}$), located in the apse.

Architectural and Structural Components

The square of St. Peter’s is a notable architectural work representing the open arms of the church and welcoming visitors. The portico features spolia, or recycled materials such as ancient pillars. The transition from the Renaissance Greek cross to the Baroque Latin cross is a defining feature of the basilica’s history. The Latin cross extension by Maderno reflects the liturgical needs of the Counter-Reformation. Beyond the main sanctuary, the Scala Regia serves as the official entrance to the Papal Palace, designed for an elegant transition from the portico to the palace levels. The exterior environment is defined by Saint Peter’s Square ($\text{Piazza San Pietro}$), which provides a grand approach to the façade inscribed with the dedication: $\text{IN HONOREM PRINCIPIS APOST PAULUS V BURGHESIUS ROMANUS PONT MAX AN MDCXII PONT VII}$.

Archaeological Investigations and the Graves of the Apostles

Modern archaeological excavations have revealed different historical layers beneath the current basilica. These levels include structures from pre-Constantinian times, Constantinian foundations, and $16 \text{th}$-century additions. Beneath the main altar lies the underground burial level, which contains catacombs and ancient burial sites. A critical discovery occurred at the "Graffiti Wall," where an inscription was found reading $\text{Petros eni}$, which translates to "Peter is here." This repository contained a wooden box holding human skeletal remains that had been overlooked for approximately $10$ years before their recovery through an accident of fate.

Identification of the Relics of Saint Peter

The skeletal remains found at the site have been identified by the $\text{Fabbrica of St Peter's}$ as belonging to Saint Peter. The fragments recovered include portions of the cranium (skull), the left clavicle (shoulder), the left ulna (forearm), and the right humerus (upper arm). Additionally, fragments of both the right and left femurs (thigh bones) were identified. These remains are considered the physical evidence of the Apostle’s burial at the Vatican, confirming the historical and religious significance of the site as the foundation of the Petrine office.

Additional Historical Context and Significance

The statues at the top of the portico depict significant saints from the Baroque period (1600s), reflecting the beliefs of that era. Peter is represented with keys, signifying his role as the Church’s representative, while Paul is depicted with a sword, symbolizing his missionary work. This area stands on the historical grounds where Emperor Nero once held chariot races and initiated the Christian persecutions. Following the acceptance of Christianity, a church was established to memorialize Peter's death and burial.

Pope Sixtus IV and Pope Julius II were instrumental in the evolution of the basilica, with Bramante leading the initial demolition of the old structure. Maderno, a close associate of Bernini, played a key role in finalizing its design. The Vatican established its own sovereignty in 1929 under Mussolini's regime, securing the Church’s powerful status worldwide, allowing it to maintain properties across the globe. Every piece of marble in the church, often sourced via spolia, showcases artistry rooted deep in history. Bernini’s designs include optical illusions that enhance the church's appearance, and the double-shell dome remains a definitive yet incomplete architectural feature. Additionally, the mosaics throughout the church not only beautify the space but also serve as reminders of the historical relics believed to be present, connecting contemporary worshippers with those who have passed.