Nobody knows the exact date but it is believed the Baroque monument was damaged during the summer.

Bernini's Fountain of the Four Rivers in Piazza Navona has been damaged but nobody appears to know who is responsible or when the incident took place, reports Huffington Post.

The face of the Nile lion belonging to the 17th-century Fontana dei Quattro Fiumi is missing its lower jaw, together with teeth, tongue and the hair under its chin.

The damage was highlighted by the art historian Martin Raspe of the Hertziana Library in Rome, in an article by Teodoro De Giorgio in the Huffington Post, and reported subsequently by Artslife and Finestre sull'Arte.

• Bernini guide to Rome

It is not known when the damage occurred: De Giorgio carried out a search among hundreds of photographs available on the internet and found that on 21 June the lion's jaw was still intact.

There are various interpretations over when exactly the lion lost its jaw, with some people suggesting that the sculpture was still intact on 23 July but already damaged by 27 August, reports Finestre sull'Arte.

• Rome fountain vandalised in Piazza Navona

The fact remains, however, that nobody seems to have noticed, or reported, when the masterpiece was damaged or where the missing fragment is now. “It is essential to find it”, writes De Giorgio in Huffington Post, “to proceed, without wasting further time, with the restoration.”

The incident also raises questions about the surveillance of the Baroque monument, one of Rome's most majestic and most-photographed fountains.

With the exception of Dr Raspe, who reported the damage as soon as he became aware, De Giorgio asks why nobody else appears to have noticed, adding pointedly that the city's superintendence for cultural heritage is based at Palazzo Braschi, a stone's throw away from the fountain.

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The apparent lack of awareness is compounded by the fact that the city staged an elaborate video-mapping light show on the fountain over the Christmas holidays, (defined by De Giorgio as an “indecent spectacle that insults the memory of the most important Baroque artist and equates Rome with Las Vegas.”)

As Finestre sull'Arte writes: "Now the most urgent hope is that the missing fragment will be found, understand who has damaged the work, and above all understand why no one has noticed."

Piazza Navona 03.00 on 13 July. Tourists swimming in Bernini's 17th-century fountain. Ph. Victoria Wyatt. pic.twitter.com/VYT2FWwcFr

— Wanted in Rome (@wantedinrome) July 13, 2015

In recent years there have been numerous cases of people swimming in the waters of the fountain, some caught and fined by police, others not.

In one incident in 2013 around 20 foreign tourists splashed about in the fountain, with one girl photographed sitting on the fragile tail of the dragon.

A similar incident made international headlines in 2015 when three American tourists swam in the fountain's waters for around 20 minutes, without being arrested.

Cover photo: Finestre sull'Arte. Image on left: the whole lion (ph. Francesco Bini, 2006), on the right the lion without the jaw (ph. @Larissaromeguide via Instagram, 5 December 2020).