Part of the ceiling over the palace of the Roman emperor Nero has collapsed in Rome, prompting fresh concerns over the stability of the ancient complex.
The damaged section at the Domus Aurea (House of Gold) complex was about 60 sq m (645 sq ft), officials say. No-one was injured.
Art official Antonello Vodret said it was one of the biggest collapses at the monument in the past 50 years.
Officials believe it was caused by water damage.
The collapse of the tunnel section of Hadrian's Baths, on top of the House of Gold, happened at about 1000 local time on Tuesday, officials said.
"Think 2,000 years of history, think of all the rain of the past couple of months," Umberto Broccoli, another Rome art official, told reporters.
The Domus Aurea had been closed for restoration when the incident happened.
The complex - located between the Colosseum and the Roman Forum - is popular with tourists.
Completed in AD68 - the year Nero committed suicide - the sprawling palace was called the House of Gold because of the amount of gold leaf which adorned much of it.
Its vaulted ceilings were once encrusted with pearls and covered in ivory, and its maze of passageways are lined with frescoes.
The complex reopened in 1999, after being shut for 18 years for restoration work amid concerns over structural problems and water infiltration. It was briefly closed to the public again in 2001, after part of a ceiling collapsed.
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