Daily Updates
Week Eight: 11 November
11 November. Minkun Zhang Reporting
Hadrian's Pantheon is one of the boldest and most original architectural creations in Roman history. The Pantheon was so technically advanced relative to its era that the roof held the world record for the longest concrete span until 1958. Today, the Pantheon is the most completely preserved building of the Imperial Roman capital. Build under the Hadrian's reign around 118 to 125 AD, and consecrated as a church in 609, the Pantheon is still in use today as a fully functional church.
The Pantheon consists of three main sections, the porch, the intermediate block, and the rotunda. The porch has the appearance of a traditional rectangular Roman temple. Situated on a podium, eight Corinthian facade columns adorn the front. Behind this facade, eight more identical columns form three aisles that leads to the entrance to the rotunda and two apses where statues of Agrippa and Augustus once stood. The roof, now made of wooden trusses and tiles, once boasted over 200 tons of bronze trusses that were later removed by Pope Urban VIII. The floor is paved in squares and a line of circles leading to the entrance of the rotunda. The intermediate block is a rectangular block of brick and concrete that connects the porch to the rotunda. Its exterior was faced with marble, and the interior consisted of vaulted chambers in the upper stories for structural support. Walking past the classic temple architecture, one leaves the traditional setting and enters a revolutionary concrete domed rotunda with an oculus in the center. Geometrically, the rotunda is a hemisphere on top of a cylinder. The dimensions of the hemisphere and cylinder are exact so that the hemisphere, with a radius of 75 roman feet, can fit perfectly inside the cylinder. The apex of the concrete dome is exactly 150 Roman feet from ground level. This engineering marvel is possible with concrete, as 90% of the intermediate block and the rotunda is made out of concrete. The engineers used concrete of different masses to build the Pantheon, utilizing heavier aggregates on bottom levels and lighter aggregates up the dome. This helps decrease the stress on the structure. The weight of the superstructure is supported and distributed downward by large brick vaults inside the rotunda walls on to eight giant piers. These piers, along with a honeycomb system of carefully placed vaults and arches inside the rotunda walls, have held the structure intact for over 1800 years. The rotunda is a centralized building; there is a vertical axis from where the building is build around. When one enters the rotunda, the vertical symmetry almost forces one to look up. The rotunda interior is lined with seven alcoves alternating in rectangular and semi-circular niches. Each alcove is screened by a pair of columns that help support the aforementioned system of interior vaults and arches. The floor design of circle and squares corresponds with the porch floor layout to guide the visitors to walk in a circle instead of a straight line. A veneering of small circles and rectangles adorn the walls and trick the naked eye into thinking the building is bigger than it is. The dome interior has five rows of 28 coffers surrounding the oculus. The coffers have enboxed sides that recede slanting inward, creating the optical illusion that the dome is more spacious. Scholars agreed that the Pantheon is a temple, most likely dedicated to all the gods. However, no one can explain why the Pantheon was never mentioned in ancient sources. After the fall of the Roman Empire, the Pantheon's survival was aided by its conversion into a church. Even today, its official name is Basilica de Sancta Maria ad Martyres. Famous Italians, such as Raphael and Victor Emmanuel II, are buried inside the Pantheon. The Pantheon's ambitious design inspired many buildings worldwide. The rotunda preceded by a rectangular structure can be found at places such as Monticello, The Library Rotunda of UVA, and the Church of St. Francesco di Paola in Naples. Works Cited: Macdonald. William, L. The Pantheon. Boston: Harvard University Press. 1976.
The octastyle porch serves as the only entrance of the Pantheon. Right behind the pediment is the intermediate block and the rotunda. A portion of the dome exterior is also visible.
The inscription on the entablature reads: Marcus Agrippa, son of Lucius, three times consul, built this. Eight Corinthian facade columns hold up the pediment. Behind the eight columns, eight more of the same design and size create three aisles that lead to the entrance and two apses.
Floor plan of the Pantheon. The black circles represent columns. The red circles and blue squares represent floor patterns. The linear path of the circles of the porch diverges off into diagonals as one enters the rotunda. This encourages visitors to move around the rotunda instead of directly forward. The yellow blocks that line the walls are the eight main piers that help support the structure. Also, note the alternate circular and rectangular alcoves. (Image after W. L Macdonald 1976, pg. 21)
The entablature lies on the Corinthian columns on the porch. Note the arches and piers system on top of the entablature designed to support the wooden roof.
Cross sectional view of the rotunda wall and dome. The projecting points mark the cornices. The types of concrete are represented on different sections of the wall. The numbers represent the densities of the concrete. (Image after W. L Macdonald 1976, pg. 31)
Exterior view of the rotunda. Note the outlines of the brick vaults that are inside the rotunda walls.
Drawing of the hollow chambers inside the rotunda walls. Note that the columns that screen the alcoves are supporting the three pairs of arches inside the brick vault. This complex system of vaults, piers, and arches is responsible for supporting the superstructure. (Image after W. L Macdonald 1976, pg. 32)
The interior of the rotunda. Each aedicule marks where one of the eight great piers is located. Also, note the rectangular and semi-circular alcoves.
The entrance to the rotunda is bordered by an aedicule on each side.
The oculus and the coffers, the oculus is the only light source for the rotunda. The spot of light moves around the rotunda during the day just like the sun moves across the sky.
The niche under the aedicule is where Raphael is buried.