Grotta del Cane

Cave of Dogs

Useful Information

The Cave of Dogs near Puzzuoli, Italy. A guide shows a suffocated dog to a man and woman tourist. Arthur Mangin, L'air et le monde aèrien, 1865, p 162. Public Domain.
Grotta del Cane. Note the visitor with a dog in the cave and a second dog in the lake in front. Public Domain.
Location: Via Raffaele Ruggiero, Agnano, Campi Flegrei, Pozzuoli, Napoli. Behind the Terme d'Agnano Hotel.
(40.829088994473330, 14.177280003906750)
Open: closed.
Fee: closed.
Classification: SpeleologyKarst Cave SpeleologyDog's Cave
Light: LightIncandescent Electric Light System
Dimension: L=9 m. H=2 m, W=1.1m
Guided tours: self guided
Photography: allowed
Accessibility: no
Bibliography: Ester Majo (1927): I fenomeni vulcanici della grotta del Cane (Campi Flegrei) in rapporto alle variazioni atmosferiche. In: Bulletin Volcanologique. 1927, 4, 1, S. 84-92, doi:10.1007/BF02719519 Springer DOI pdf
Alfred Swaine Taylor (1832): An Account of the Grotta del Cane With Remarks Upon Suffocation by Carbonic Acid, The London Medical and Physical Journal, 1832, 278-285. pdf
William R Halliday, Arrigo A Cigna (2006): The Grotta Del Cane (Dog Cave), Naples, Italy Cave and Karst Science, 2006, Transactions of the British Cave Rescarch Association. 33 (3): pp 134–136. pdf researchgate
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


77 AD first mentioned by Pliny the Elder in Naturalis Historia.
1638 first scientific study of the cave by Athanasius Kircher.
13-JUN-1781 visited by Wolfgang Amadeus Mozart.
01-MAR-1787 visited by Johann Wolfgang von Goethe.
1804 visited by Washington Irving.
1818 visited by Mary Shelley.
1833 visited by Ralph Waldo Emerson.
1867 visited by Mark Twain.
1870 polluted lake drained, visitor numbers drop massively.
1930s experiment forbidden by law due for cruelty to animals.
1960s cave walled and forgotten.
1989 rediscovered by Abignente and Feniello from the Gruppo Speleologico della sezione napoletana, a section of the Club Alpino Italiano.
1998 the associazione Conca di Agnano led by Professor Silvana Russo started the restauration of the historic place.
2001 debris and bushes cleaned, cave again accessible, but not open to the public.
2013 Scientific exploration of the carbon dioxide amount and the temperature in the cave by Napoli Underground.


The principle of the Cave of Dogs sketched by Taylor, The London Medical and Physical Journal, 1832. Public Domain.
Le Lac d'Agnano. Pierre Vander, Les délices de l’Italie, Vol. III, Leida, 1706. Public Domain.

The Grotta del Cane (Dogs Cave) is not really a cave, it's a volcanic feature called mofetta or fumarole, a volcanic discharge of carbon dioxide (CO2). This source of carbon dioxide is located inside a small hollow, a tiny artificial passage, which is only 9 m long. The important fact is: the floor is going down to the inside. So a shallow lake of about 30 cm of almost pure carbon dioxide, which is heavier than normal air, forms inside the cave. Italian speleologists measured a temperature of 52 °C and a carbon dioxide concentration of 80 %, with negligible oxygen at the end of the passage. People entering the cave accompanied by a dog do not feel any difference, because their head is above the carbon dioxide lake, but the dog suffocates due to the lack of oxygen. The dog collapses and if not removed from the grotto will soon die of asphyxiation. Carbon dioxid is actually not poisonous, the problem is just the lack of oxygen.

Such a strange place was mentioned as early as the Roman times, it was described by Pliny the Elder (lib. 2, c. 90). This tells us, it was dug more than 2,000 years ago. But the reason why it was created is unknown the reasons why the excavation was stopped also. But it seems obvious that they stopped because of the heat and the carbon dioxide. It became very popular with the first flood of Italy-tourism during the 19th century, the so-called Grand Tour. At this time the experiment was actually made with a dog, which was frequently rescued before it died. It seems the animal became used to being suffocated. The other version of the story, after which the dog was sent in to die, is a little cynical, and we don't think it was very practical to kill the dog with every demonstration. Probably the visitors were just overwhelmed and did not notice the dog was just senseless. Probably the guides exaggerated the dangers of the cave. Some tourists objected to the cruelty, and refused to pay for the experiment to be performed on the dog.

Grotta del Cane (Dog Cave) (Naples). The Dog's Cave, so called from the practice of sending dogs into it to show visitors how the carbonic acid gas near the floor of the cave kills them.

Text by E. Cobham Brewer (1894): Dictionary of Phrase and Fable.

Nero's Baths, the ruins of Baiae, the Temple of Serapis; Cumae, where the Cumaen Sybil interpreted the oracles, the Lake Agnano, with its ancient submerged city still visible far down in its depths-these and a hundred other points of interest we examined with critical imbecility, but the Grotto of the Dog claimed our chief attention, because we had heard and read so much about it. Every body has written about the Grotto del Cane and its poisonous vapors, from Pliny down to Smith, and every tourist has held a dog over its floor by the legs to test the capabilities of the place. The dog dies in a minute and a half-a chicken instantly. As a general thing, strangers who crawl in there to sleep do not get up until they are called. And then they don't either. The stranger that ventures to sleep there takes a permanent contract. I longed to see this grotto. I resolved to take a dog and hold him myself; suffocate him a little, and time him; suffocate him some more and then finish him. We reached the grotto at about three in the afternoon, and proceeded at once to make the experiments. But now, an important difficulty presented itself. We had no dog.

Text by Mark Twain (1869): The Innocents Abroad: Chapter XXX..

Today the Solfatara at Pozzuoli is the most popular tourist site of the Campi Flegrei, showing numerous volcanic features. It is actually the only part of the volcanism which is open to the public. The Grotta del Cane is located only a kilometer away. According to old engravings, it is located at the southern shore of Lake Agnano. However, this lake has vanished since the 19th century engravings were made. Lake Agnano was drained, most likely because it was a source of malaria, but also, because it was polluted, and probably to use the land for agriculture. This was around 1870. Today it is a plain called Agnano Basin or Agnano Crater. The cave is located at the southeastern rim.

While the cave was frequently visited until the late 19th century, it was obviously forgotten or abandoned at some point. When exactly is unknown, there are different times and reasons given in literature. Then there came the two World Wars, and it seems at one point it was not reopened, although one source states it was banned before World War II for cruelty to animals. At that time, the cave entrance was walled up to prevent accidents. The place was rather inaccessible, and so the property around the entrance became a popular place for drug addicts in the mid-20th century, Finally, the Gruppo Speleologico della sezione napoletana rediscovered the cave in 1989. After some research and some publication of the results, an initiative of local citizens removed the growing bushes and the rubbish in 2001. We guess, they also wanted to make the site inhospitable to the drug addicts, which was successful.

The dipartimento delle Scienze della Terra (Department of Earth Sciences) of the facoltà degli studi di Napoli Federico II (University of Naples Federico II) plans to create a Parco Geologico (geologic park), which would include the dog cave, but so far the communal politicians were not willing to support such a project. Professor Vincenzo Morra, the former director of the Ordine dei geologi della Campania (Order of the Geologists of Campania) suggests an Parco Museo Ipogeo (underground museum park) in this area. There are numerous interesting underground sites which allow a view into the local geology. However, none of this happened so far, and the cave is still not accessible. Nevertheless, this cave is of great historical and cultural importance and deserves to be listed anyway.