The Pantheon (meaning 'temple of every god') is a former Roman temple, now a church, on the site of an earlier temple commissioned by Marcus Agrippa during the reign of Augustus (27 BC-14 AD). The present building was completed by the emperor Hadrian and probably dedicated about 126 AD. He retained Agrippa's original inscription, which has confused its date of construction as the original Pantheon burnt down so it is not certain when the present one was built.
The building is circular with a portico of large granite Corinthian columns under a pediment. A rectangular vestibule links the porch to the rotunda, which is under a coffered concrete dome, with a central opening (oculus) to the sky. Almost two thousand years after it was built, the Pantheon's dome is still the world's largest unreinforced concrete dome. The height to the oculus and the diameter of the interior circle are the same, 43.3 metres.
Pantheon is one of the best-preserved of all Ancient Roman buildings. The Pantheon's large circular domed cella, with a conventional temple portico front, is 'unique' in Roman architecture. Nevertheless, it became a standard exemplar when classical styles were revived, and has been copied many times by modern architects.
Pantheon was converted into the church of St. Mary of the Martyrs in 608 CE. In 1270 a bell tower was added to the porch roof and later removed. Also, at some time in the Middle Ages the left side of the porch was damaged which necessitated the replacement of three columns. The first came from Domitian's villa at Castelgandolfo and was added in 1626. The other two columns came from the Baths of Nero and were added in 1666. However, these additions were rose-pink in colour whilst originally the front eight columns of the porch were all grey and only the internal four were pink Aswan. Also in 1626 Pope Urban VIII removed all of the bronze girders from the porch roof and recast the metal into 80 canons for the city's Castel Sant'Angelo. The presence of these girders suggests that the porch roof originally had heavy marble tiles.
Despite these changes the Pantheon is one of the best preserved ancient monuments in the world and it still has an important function and status today as within it are the tombs of the Italian monarchy from 1870-1946 and another notable tomb is that of Raphael (1483-1520 CE).
Pantheon is visited by over 6 million people annually. It is part of the UNESCO World Heritage Site Historic Centre of Rome.References:
The Porta Nigra (Latin for black gate) is the largest Roman city gate north of the Alps. It is designated as part of the Roman Monuments, Cathedral of St. Peter and Church of Our Lady in Trier UNESCO World Heritage Site. The name Porta Nigra originated in the Middle Ages due to the darkened colour of its stone; the original Roman name has not been preserved. Locals commonly refer to the Porta Nigra simply as Porta.
The Porta Nigra was built in grey sandstone between 186 and 200 AD. The original gate consisted of two four-storied towers, projecting as near semicircles on the outer side. A narrow courtyard separated the two gate openings on either side. For unknown reasons, however, the construction of the gate remained unfinished. For example, the stones at the northern (outer) side of the gate were never abraded, and the protruding stones would have made it impossible to install movable gates. Nonetheless, the gate was used for several centuries until the end of the Roman era in Trier.
In Roman times, the Porta Nigra was part of a system of four city gates, one of which stood at each side of the roughly rectangular Roman city. The Porta Nigra guarded the northern entry to the Roman city, while the Porta Alba (White Gate) was built in the east, the Porta Media (Middle Gate) in the south, and the Porta Inclyta (Famous Gate) in the west, next to the Roman bridge across the Moselle. The gates stood at the ends of the two main streets of the Roman Trier, one of which led north-south and the other east-west. Of these gates, only the Porta Nigra still exists today.
In the early Middle Ages the Roman city gates were no longer used for their original function and their stones were taken and reused for other buildings. Also iron and lead braces were broken out of the walls of the Porta Nigra for reuse. Traces of this destruction are still clearly visible on the north side of the gate.
After 1028, the Greek monk Simeon lived as a hermit in the ruins of the Porta Nigra. After his death (1035) and sanctification, the Simeonstift monastery was built next to the Porta Nigra to honor him. Saving it from further destruction, the Porta Nigra was transformed into a church: The inner court of the gate was roofed and intermediate ceilings were inserted. The two middle storeys of the former gate were converted into church naves: the upper storey being for the monks and the lower storey for the general public. The ground floor with the large gates was sealed, and a large outside staircase was constructed alongside the south side (the town side) of the gate, up to the lower storey of the church. A small staircase led further up to the upper storey. The church rooms were accessible through former windows of the western tower of the Porta Nigra that were enlarged to become entrance doors (still visible today). The top floor of the western tower was used as church tower, the eastern tower was leveled, and an apse added at its east side. An additional gate - the much smaller Simeon Gate - was built adjacent to the East side of the Porta Nigra and served as a city gate in medieval times.
In 1802 Napoleon Bonaparte dissolved the church in the Porta Nigra and the monastery beside it, along with the vast majority of Trier"s numerous churches and monasteries. On his visit to Trier in 1804, Napoleon ordered that the Porta Nigra be converted back to its Roman form. Only the apse was kept; but the eastern tower was not rebuilt to its original height. Local legend has it that Napoleon originally wanted to completely tear down the church, but locals convinced him that the church had actually been a Gaulish festival hall before being turned into a church. Another version of the story is that they told him about its Roman origins, persuading him to convert the gate back to its original form.
In 1986 the Porta Nigra was designated a World Heritage Site, along with other Roman monuments in Trier and its surroundings. The modern appearance of the Porta Nigra goes back almost unchanged to the reconstruction ordered by Napoleon. At the south side of the Porta Nigra, remains of Roman columns line the last 100 m of the street leading to the gate. Positioned where they had stood in Roman times, they give a slight impression of the aspect of the original Roman street that was lined with colonnades. The Porta Nigra, including the upper floors, is open to visitors.