What is the purpose of the oculus in the Pantheon?

The oculus in the Pantheon serves the primary purpose of allowing natural light to enter the interior space of the structure. This feature creates a dynamic interplay of light and shadow throughout the day, illuminating the interior while connecting the earthly realm within the building to the heavens above. The oculus, measuring about 8.2 meters (27 feet) in diameter, is the only source of natural light in the Pantheon, and its placement directly in the center of the dome emphasizes the architectural harmony and beauty of the space.

Additionally, the oculus has an important symbolic role, representing the sun and serving a spiritual function in connecting visitors to the divine. While the other options touch on relevant aspects of architecture, such as ventilation or decoration, they do not capture the fundamental role of the oculus as the primary means of lighting the vast interior of the Pantheon. The structural integrity and support of the dome are primarily achieved through the careful design and engineering of materials rather than through the function of the oculus.