lantern
lantern
Old French
“The small tower at the top of a dome — the lantern that lets light into the interior — is named for the object that carries light. The architectural lantern and the handheld lantern are the same word, because both admit light through an enclosed framework.”
Old French lanterne — a portable light with a protected flame — comes from Latin lanterna, which comes from Greek lampter (torch, lamp). The Greek lamp gave its name to a protective enclosure, and the enclosure became the word. The architectural lantern — a small tower with windows placed at the apex of a dome — was so named because it admits light into the dark space below, exactly as a handheld lantern admits light into darkness.
The dome lantern appeared in Italian Renaissance architecture as the solution to a problem: a dome blocks light from reaching the interior. Brunelleschi's lantern on the Florence Cathedral dome (1436) was not just decorative — it provided structural compression at the dome's crown and admitted light through its windows. Brunelleschi had to fight the Opera del Duomo to build the lantern he had designed, as some felt the opening was structurally risky.
Michelangelo's design for the lantern of St. Peter's Basilica in Rome was modified after his death, to his specifications' detriment according to later critics. The St. Peter's lantern weighs approximately 700 tonnes — a massive addition to the dome that required the drum below to be made extraordinarily strong. The light-admitting tower that crowns a dome is also the structure that most threatens to crush it.
The Pantheon in Rome (118-128 CE) has no lantern — its single light source is the oculus, an open 9-meter hole in the dome's apex. The oculus admits rain, which drains through holes in the floor; it admits a beam of light that moves around the interior as the Earth rotates. The Pantheon chose unmediated sky over an enclosed lantern. The choice defines the building's character.
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Today
The lantern is where the building ends and the sky begins. Every dome lantern — Florence, Rome, London — is an architectural decision about the threshold between human construction and the sky above. The Pantheon made the threshold a hole; Brunelleschi enclosed it in stone; both choices define how light enters and how the interior feels.
The 700-tonne lantern on St. Peter's may outlast the dome it crowns. The ancient Roman concrete of the Pantheon's dome has survived 1,900 years; the Renaissance masonry of St. Peter's is already requiring repair. The lantern that was meant to complete the dome may survive the building it was designed to top.
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