Vatican researchers have scaled the cupola atop St. Peter's Basilica
to use high-tech tools to study the dome's innards and found the
structure to be more sturdily built than experts had long believed, the
Vatican's newspaper said Tuesday.
The research, conducted by two
members of the basilica's engineering and maintenance department, "does
not only allow us to discover the materials and techniques used for the
construction, but it allows us to learn its actual state of health,"
L'Osservatore Romano wrote.
It said the research found that the
16th-century equivalent of today's reinforcement concrete was used to
construct the dome, which was largely based on a design by Michelangelo.
Before
the project began, researchers combed art historians' writings, but
concluded they "presented numerous inaccuracies," since much was based
on either oral tradition or on accounts that were never verified,
L'Osservatore said.
The basilica office was closed for the day, and the researchers could not be reached for elaboration.
One
of the researchers climbed the dome "like an Alpine mountaineer," and,
armed with geo-radar, discovered seven internal iron rings used to hold
the travertine stone together, the report said. Scholars, using
centuries-old documents, had thought only two rings were used to girdle
the structure, it added.
The Vatican says the dome, topped by a
cross which towers 520-foot (136.5-meters) above the ground, seems to
have been even more sturdily constructed than long believed.
Using
techniques of the latter 16th century, the builders "used a system of
reinforcement similar to modern reinforced concrete," the researchers
concluded, according to L'Osservatore.
Iron chains, set at various
heights, helped reinforce the stability of the cupola, to the likely
relief of countless tourists who have made the dizzying climb inside the
dome to admire the view from the top.
L'Osservatore said
researcher Marta Carusi, scanning the dome's walls with a geo-radar
device, determined "the exact position of girdling rings, bars and
chains" used to keep the dome stable.
"Hidden inside the walls,
these materials weren't able to be pinpointed and the memory of (their
use in construction) had been lost," the paper said.
The geo-radar
exam, which involves electromagnetic impulses and echoes, allowed
experts to find many more metallic underpinnings than long believed, the
paper said.