With its remarkable dome, the Pantheon ranks as one of the great architectural marvels of ancient Rome. The building derives its beauty and harmony from its geometrical purity. Like an orange cut in half, the dome is a hemisphere. Unlike a halved orange, though, it is perfect: The dome's diameter is precisely the same as its height from the floor at about 142 feet.

In the center of the dome, a round eye opens to the sky. This oculus, an aperture measuring 27 feet across, admits a stream of sunlight -- the building's only source of illumination. During shadow and storm, the oculus reveals oddly beautiful special effects in the celestial fragment that appears.

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All lighting in the Pantheon is natural, entering through the 27-foot oculus in the dome.
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Although the Pantheon's exterior may get
most of the attention, its interior houses
many treasures of its own.
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The hole seems to connect the Pantheon to the sky and stars above -- an impression that is only fitting, as the building was dedicated to Rome's planetary deities. Completed around A.D. 120, the Pantheon was rededicated as a Christian church some 500 years later. This move no doubt helped to protect the site and probably explains why the Pantheon is the most complete and best-preserved building from imperial Rome.

The Pantheon's original bronze doors still survive, standing 24 feet high. In Roman days the interior was richly decorated. Niches held figures of deities, and a statue of Jupiter, Rome's primary god, stood in the center, illuminated at noon by a shaft of light from the oculus overhead.

The ancient dome is literally superlative: the largest cast-concrete construction on Earth until the 20th century. (At 142 feet across, it beats the dome of St. Peter's Basilica by six feet.) But how is the whole thing supported? No arches show, because they were embedded inside the 20-foot-thick walls, where they function like buttresses. And the dome's weight was reduced by using hollow, decorative coffering inside.

It is no wonder that the Pantheon, a surviving remnant of a world long vanished, still inspires architects to this day.

Here are links to dozens of other world-famous landmarks:

Abu Simbel, EgyptEiffel Tower, FranceThe Leaning Tower of Pisa, ItalyRoman and Georgian Bath, England
The Alhambra, SpainEllora Caves, IndiaMachu Picchu, PeruSt. Mark’s Basilica, Italy
Angkor Wat, CambodiaThe Forbidden City, ChinaMont-St.-Michel, FranceSt. Paul’s Cathedral, England
Arc de Triomphe, FranceThe Golden Pavilion, JapanNeuschwanstein Castle, GermanySt. Peter’s Basilica and the Sistine Chapel, Italy
Borobudur, IndonesiaThe Great Buddha, JapanPalace of Versailles, FranceShwedagon Pagoda, Myanmar
Chartres Cathedral, FranceThe Great Wall of China, ChinaThe Pantheon, ItalyStonehenge, England
Christ the Redeemer Statue, BrazilGuggenheim Museum, Bilbao, SpainThe Parthenon and the Acropolis, GreeceSydney Opera House, Australia
CN Tower, CanadaHagia Sophia, TurkeyPetra, JordanThe Taj Mahal, India
The Colosseum, ItalyHouses of Parliament, EnglandPompeii, ItalyThe Temple at Karnak, Egypt
The Dome of the Rock, IsraelThe Kaaba and Al-Haram Mosque, Saudi ArabiaPotala Palace, ChinaThe Terra-cotta Army, China
Easter Island Statues, ChileKrak des Chevaliers, SyriaThe Pyramids of Giza and the Great Sphinx, Egypt
Edinburgh Castle, ScotlandThe Kremlin and Red Square, RussiaPyramids of the Sun and Moon at Teotihuac√°n, Mexico


To learn more about other landmarks and vacation destinations, see:

ABOUT THE AUTHOR:

Jerry Camarillo Dunn, Jr., has worked with the National Geographic Society for more than 20 years, starting as a staff editor, writer, and columnist at Traveler magazine, then writing travel guides. His latest work is National Geographic Traveler: San Francisco. Dunn’s Smithsonian Guide to Historic America: The Rocky Mountain States has sold more than 100,000 copies. His travel pieces appear in newspapers such as the Chicago Tribune and The Boston Globe. Jerry Dunn's stories have won three Lowell Thomas Awards from the Society of American Travel Writers -- the highest honor in the field. He also wrote and hosted a pilot episode for a travel show produced by WGBH, Boston's public television station.