The sprawling third-century Baths of Caracalla in Rome were damaged by the earthquake that ravaged central Italy on Monday, a city archaeological authority told reporters.
The baths "suffered some damage," Angelo Bottini said, adding that the results of an initial inspection had "not yet been precisely evaluated."
The red-brick ruins, which cover some 11 hectares (27 acres) at the foot of Rome's Aventine Hill, are the frequent site of opera productions and open-air concerts in the summer.
During Emperor Caracalla's era, the bathing facilities could accommodate more than 1,600 people and included gymnasiums, libraries and gardens.
Bottini said no other historic sites in the Eternal City were damaged.
The quake that claimed at least 50 lives in the Abruzzo region northwest of Rome woke many residents of the Italian capital at shortly after 3:30 am (0130 GMT).
In the quake's epicentre, the Abruzzo capital L'Aquila, the dome of a church fell in and the city's main San Massimo cathedral was damaged.
The cathedral was initially built in the 13th century, but was destroyed in an earthquake early in the 18th century.
The present facade dates to 1851 and has two bell towers in the neo-classical style.