The Pantheon dome is the world’s largest unreinforced concrete dome, measuring 43.3 meters (142 feet) in diameter and 21.75 meters (71 feet) in height.
Founded over 2000 years ago by the Roman emperor Hadrian, the Dome of the Pantheon is notable for its size, construction, and design.
It is the only masonry dome not to require reinforcement and has inspired architects and engineers for centuries.
The dome is also notable for its central oculus, a 9-meter (30-foot)-wide opening in the center that allows natural light to enter the interior.
It is a testament to the skill and creativity of the ancient Romans and remains one of the most impressive architectural feats of all time.
Originally dedicated to Roman gods, it is today a living testament to ancient Roman architecture.
Pantheon Dome facts
Date of Opening: 126 AD
Dome’s Dimensions: Height and diameter of 43 meters (142 feet)
Architects: Marcus Agrippa (original) and Apollodorus of Damascus (reconstruction)
Architectural Style: Roman Classical
UNESCO World Heritage Site: Designated in 1980
Visitors per year: approximately 7 million
Notable Feature: It is the world’s largest unreinforced concrete dome
What makes the Pantheon Dome special
The Pantheon dome is special for many reasons.
First, it is the largest unreinforced concrete dome in the world. It is over 2,000 years old and has stood the test despite being built without modern engineering techniques.
Second, it is perfectly symmetrical. This is a remarkable feat for such a large structure, and it demonstrates the skill of the Roman builders.
Third, the Pantheon dome structure is very efficient. It is designed to distribute the weight evenly, making it strong and stable.
Fourth, the dome is beautiful. It is a perfect example of Roman architecture and one of Rome’s most iconic landmarks.
Pantheon Dome Highlights

The Coffers
The Pantheon dome interior has a series of recessed panels known as coffers.
These coffers have a dual function: adding elegance to its interior and diminishing the dome’s overall weight.
The five rows of twenty-eight coffers ensure an even distribution of forces, improving stability.
Oculus
The oculus stands out as one of the most remarkable and distinctive elements in the Dome of the Pantheon.
Its circular opening at the dome’s apex is designed to let sunlight and rain into the building.
It has a diameter of 8.8 meters (29 feet) and is the sole provider of natural light within the Pantheon, apart from the entry door.
Rotunda
Roman builders constructed a solid base, a wall six meters thick in the shape of a rotunda, to act as the foundation for the ceiling.
They then used the vertical walls on either side to support the Pantheon’s dome.
They mixed increasingly lighter aggregate materials into the concrete as the ceiling rose toward its apex.
To make the ceiling even lighter, they molded recessed concrete waffle-like panel bricks called coffers in five layers, forming the interior ceiling.
If you want to know about the architecture of the Pantheon, you can read our article to learn about it in detail.
Pantheon Dome construction: Secret behind the stability
The enduring strength of the dome lies in the innovative use of concrete.
Though the Romans were not the inventors of concrete, they followed a recipe outlined by the architect Vitruvius.
They mixed lime, pozzolana sand, and various aggregates, creating a versatile material with different densities.
The foundations, made of travertine limestone, ensured stability, while lighter materials like tuff and pumice were used for the dome’s upper layers.
The unique challenge was supporting the massive dome without collapsing under its weight.
The builders used a circular structure with thick walls, gradually incorporating lighter materials as the dome rose.
The clever addition of recessed panel bricks called coffers reduced the amount of concrete needed and added an aesthetic touch.
One of the most extraordinary features is the open oculus at the dome’s apex, which allows light to flood in.
This final touch made the dome more unique and, to date, acts as the most crucial source of light inside the building.
FAQ’s
How was the Pantheon Dome built?
The Roman builders used an innovative concrete recipe, combining lime, pozzolana sand, and various aggregates. They created a versatile material with different densities, constructing a circular structure with gradually lighter materials as the dome rose. To ensure stability, they built a solid base and a six-meter-thick wall shaped like a rotunda, supported by vertical walls on either side. The addition of recessed panel bricks, or coffers, reduced the weight, contributing to the dome’s overall stability.
What keeps the massive dome of the Pantheon from collapsing?
The massive dome of the Pantheon is prevented from collapsing by a combination of its circular structure, thick supporting walls, and the innovative use of materials. Additionally, including recessed panel bricks called coffers reduced the overall weight and contributed to the dome’s stability.
What is the Pantheon dome made of?
The Dome of the Pantheon Rome is made of a concrete mixture created with basic ingredients, including lime, pozzolana sand, and various aggregates. The foundation is crafted from travertine limestone, providing stability, while lighter materials like tuff and pumice were used for the upper layers of the dome.
What is unique about the Dome of the Pantheon?
The Dome of the Pantheon is unique for several reasons. It has held the record as the largest dome for an astonishing 1300 years and is currently the world’s largest unsupported concrete dome. It has perfect symmetry, with its height matching its interior circle’s diameter. The oculus, a circular opening at the dome’s apex that lets rain and sunlight in, adds to its uniqueness and charm.
Who built the Pantheon dome?
Marcus Agrippa commissioned the original Pantheon. But the current dome is a reconstruction by Apollodorus of Damascus, commissioned by Emperor Hadrian in 126 AD.
What is the oldest dome in the world?
The Pantheon Dome is the world’s oldest and most iconic dome, dating back to its construction in 126 AD.
Are there cracks in the Pantheon in Rome?
Yes, there are cracks in the Pantheon dome. The cracks are not new, and they have been there for centuries. Various factors, including the weight of the dome, temperature-related concrete expansion and contraction, and foundation settlement, cause cracks.
Is the Pantheon the largest dome?
The Pantheon dome in Rome is the largest unreinforced concrete dome in the world. It is 43.3 meters (142 feet) in diameter and the same height. It has stood for nearly 2,000 years. But it is not the largest dome overall. The largest dome in the world is the Singapore National Stadium dome.