Naples:life,death &
                Miracle contact: Jeff Matthews

entry 2012

This is a detail from a 1663 print by J. Bleau and P. Mortier.

Agnano & the Grotto of the Dog
—or, Now I know why I couldn't find the Lake.

Mark Twain, adding himself to the long list of travelers to write about the infamous Grotto of the Dog, said this (in The Innocents Abroad):
Nero’s Baths, the ruins of Baiae, the Temple of Serapis; Cumae, where the Cumaean Sibyl interpreted the oracles, the Lake Agnano, with its ancient submerged city still visible far down in the 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. Everybody 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...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 about three in the afternoon...But now, an important difficulty presented itself. We had no dog.
I was sure when I read that passage that MT was wrong about the lake. There were many points of Greek and Roman interest in the area, yes, but there was no Lake Agnano! Hmph! Sage of Hannibal, indeed. I was outraged and triumphant at the same time! Oops...(speaking of critical imbeciles), I missed it by a century and a bit, but at the time MT was there, there was indeed a Lake Agnano. It was drained in 1870, a short time after he passed through. It was not one of the myth-shrouded lakes of ancient times (such as Lake Averno) but had been around only since about 1100 AD when seismic shenanigans created it in the middle of the Agnano basin. The Agnano basin is on the eastern side of the Campi Flegrei, the volcanic remnants of the event that produced the great Archiflegrean caldera collapse about 40,000 years ago. The area shown in the  above map is about 30 km across. The Archiflegrean caldera is the area bounded by the red lines with wedges. The Agnano basin is labelled "Agnano." The lake filled much of the basin. The Grotto of the Dog is about where the letter o is in the word Agnano. (There is now a large and very popular horse-racing track right above the word Agnano!)

(paragraph below added, Nov. 2014)

What the Agnano basin was like before the lake formed in the 11th century is speculative. The following is excerpted (with permission) from The Ancient Thermal Baths of Agnano & the Grotto of the Dog by Selene Salvi of Napoli Underground (NUg). The entire article is on the NUg website at this link. (As of 2019, that site is not active. Sorry.)
The Agnano basin is the oldest crater from the third eruptive period of the Flegrean Fields (8,000-3,900 years ago)...The circumference of the basin is 6.5 km. Since antiquity this site has been most commonly sought after because of its therapeutic value-that is, the presence of secondary volcanic phenomena (thermal springs, fumaroles and solfatare-i.e. sulfur vents). On the slopes of Mt. Spina you can see the ruins of Roman thermal baths dated to the 1st-2nd century AD. They consist of an apodyterium, a frigidarium, warm rooms (tepidaria, calidaria and laconica) as well as a series of interconnected cisterns. The complex was a way-station for those on the roadbetween Neapolis and Puteoli [Pozzuoli]; it was fed by the Serino aqueduct of Augustus, using, as well,  the on-site underground hot-water springs...One theory is that the [Grotto of the Dog] was hollowed out to serve primarily as a steam room or thermal bath in the 3rd-2nd century BC, at which time the infamous gas had not yet broken into the chamber or at least was somehow kept from building up within it...Another fascinating theory connects the grotto to those buildings from the Hellenic age of the 4th-3rd century BC found in the basin after the draining and land reclamation (1870): the ancient city submerged in the depths of a lake, the waters of which had had such a harmful effect on travellers over the centuries...

Measurements of the lake before was it drained showed it to be circular, 924,000 sq. meters (about 230 acres) in area, and 12-15 meters/36-45 feet deep in the middle. By the time of the draining, the lake had swamped up and turned into a vast snake- and frog-infested, foreboding place. Drying up the lake/swamp was part of land reclamation in the south by the new Italy, united in 1861. The initial work was done between 1865-70 and produced a fan-like network of narrow channels of varying length covering the basin (the lake bottom) (image, right). The channels converged and, aided by a series of pumps, moved the lake waters to the central hub (quaintly named "Fount of Apollo"!) and into a drain tunnel through Monte Spina to Bagnoli, two km away, and into the sea. The lake dried up and revealed for the first time in almost a thousand years, the large number of thermal springs, the therapeutic value of which was known in ancient times. But, indeed, the many tales over the last few centuries from travelers who visited a noxious dog-killing cave on the shores of a lake in Agnano are accurate.

It is worth emphasis that the work in 1870 was not a one-time affair. It was the beginning of a long-term project to reclaim land and manage water resources in the area. (Indeed, if they stopped managing and reclaiming, you'd wind up with another lake in no time!) New canals and drains were added over the decades, and in 1934 the Consortium for the Reclamation of the Agnano Basin was set up to oversee and continue work. Quite recently (2003) that consortium was expanded to include "...and the Flegrean Basins" for a total area of some 5,600 hectares (about 20 sq. miles). Indeed, today you can stroll along the channels of the Agnano basin and watch the dark, mineral-laden waters still wending their way towards the Fount of Apollo. (One such channel is shown in the photo, below on the right.)

(The above map comes from Larry Ray. His comments on his first impressions of this site many years ago may be viewed here.)

With the draining of the lake in 1870, the many thermal springs again became available, and for many years there has been a spa, a thermal bath establishment, the Terme d'Agnano, just below Mt. Spina at the southern end of the basin. The Agnano baths were at their height of popularity in the 1920s; the hotel and baths were housed in one of the grandest examples of Art Nouveau architecture in Naples (photo, left), built in 1910/11 and designed by Giulio Ulisse Arata. During WWII, the spa quartered the officers and nurses of the US 21st General Hospital, which was stationed there and at the nearby Mostra d'Oltremare fairgrounds from December 1943 to September, 1944; the building was demolished in 1961 and replaced with the current facility, designed by Giulio De Luca. The area degraded terribly after WWII and became an eyesore from shoddy overbuilding and illegal waste dumping. I drove by the baths hundreds of times over the years and never knew about the lake, never knew that I was 100 yards from the Grotto of the Dog and never knew that I was in the middle of an archaeological site that includes Greek stonework and a Roman thermal bath complex. No attention was paid to any of that by those who might have done something about the situation.

hat has changed. Over the past 10 years, various private groups have remade the area. The grounds of the Terme d'Agnano are pristine (photo, above left). On the premises, there is a small section of stone put in place by the Greeks (photo, above right) that has been explained as part of the foundation of a retaining wall at the base of Mt. Spina. There was probably a temple of sorts at that spot and the whole site is thought to have been a rest stop (and hot thermal bath!) at about the halfway point for those moving between Neapolis and Cuma in around 300 BC. The stones are the only bit of ancient Greek masonry in the Campi Flegrei.

The Romans, of course, enlarged the bath facilities enormously. Their site here was explored partially in the late 1800s and then documented by archaeologists in some detail by 1911. The Romans honeycombed the entire northern flank of Mt. Spina (now across the modern road from the Terme d'Agnano) with a large thermal bath complex (photo, left). It had warm rooms, hot rooms, cold rooms and cisterns supplied by the main aqueduct that ran along the top of Mt. Spina. (The aqueduct moved water to the Piscina Mirabilis and military port at Baia at the western end of the gulf.) The cisterns also stored and distributed thermal water from the natural on-site springs. It's hard to say how the thermal springs and baths fared during the dark ages following the fall of the Roman Empire. (I don't imagine that Vandals and Goths took a lot of baths, but I don't really know.) In any event, the beneficial waters of the Agnano springs took a severe blow in 1100 when the lake, itself, came into existence. It swamped over in time and the area developed a very unwholesome reputation. A 1775 map of the lake drawn by G. Carafa Duca di Noja describes it as a lake with " fish but countless frogs and entangled snakes that fall into the waters and die, accounting for the stench..."  But the lake and shore have seen some service since the middle ages; the same description says that Alfonso I of Aragon (who ruled from 1442-58) used the waters of the lake for the steeping (or retting) process in the production of linen.

Visitors to the Grotto of the Dog       
(the gate in the background, left.)
I said that the "many tales...[about]...a dog-killing cave on the shores of a lake in Agnano are accurate". Well, to a certain extent. Drawings from the 1600s and 1700s idealize the lake—no snakes or frogs! Many of them (such as the one at the top of this page) show the entrance to the Grotto of the Dog as adjacent to a thermal bath called the Le Terme di San Germano. They're not really that near each other, but I suppose it doesn't matter—Grand Tourists were allowed to liven up the truth a bit. (And MT may have been right about the lake, but, "...The Lake Agnano with its ancient submerged city still visible far down in the depths..." is stretching it a bit. He and I have agreed to call it even.) The essentials are that the grotto (that you may now see, photo, right) is behind the Terme d'Agnano Hotel. The cave is about 10 meters long with steps leading down into it. The space still fills with naturally occurring carbon dioxide from the thermal vents and hugs the ground like fog (since it is heavier than the surrounding air) in such concentrations that you can see it from the entrance; it really would knock tiny little Fido out (and possibly kill him) while leaving Owner unharmed (because his moronic head is some feet above the thick layer of CO2). But not to worry, most paintings of the fun had by all (except the dogs) show humans, yes, dragging doggies into the gas, but then throwing them in the lake to revive them. The pooches supposedly trotted out again, confused but alive.

This site was one of the 22 Royal Bourbon properties in the Kingdom of Naples. They range from the large Royal palaces to smaller residences and hunting lodges. This is the complete list with links to entries:
Palace Naples
Palace Capodimonte
Palace Portici

Palace Caserta
villa d'Elboeuf 
Villa Favorita
Palazzo d'Avalos
Lake Agnano
San Leucio
Palace Quisisana
Demanio di Calvi

repeat, many volunteers (and that includes volunteer divers with special masks!) are responsible for dredging and cleaning out the grotto as well as for clearing away waste and vegetation from the Roman site over the last few years. Among these groups are the Association for the Agnano Basin, the Naples Archaeology Group, the Speleological Research Unit of the Civil Protection Center of Naples, and the Bagnoli Hotel Training Institute. They worked in collaboration with Terme d'Agnano, Inc. and the Special Superintendency for Archaeology of Naples and Pompei. They continue to work and lead tourists to the Greek stones, the Roman baths and the Grotto of the Dog. The property of the Terme d'Agnano, itself, the modern hotel and thermal bath facility, extends for about 30 acres to the north and northeast; the area contains 75 identified thermal springs and is becoming increasingly more pleasant to visit. Bring your own dog.

This is the base page for Agnano & the Agnano thermal baths.
Other relevant entries about that site are 
(2)     (3)     (4)   (5)

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