The Bizarre Story of the Nemi Ships built by Caligula

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The Nemi Ships

The Nemi ships, 70 meters long and more than 25 meters wide, had been built by Emperor Caligula, in honor of the Egyptian goddess Isis and Diana, goddess of wild animals and the hunt.

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Since ancient times, legends circulated about two gigantic and magnificent ships, built in Roman times, which perhaps contained treasures and other fortunes, which lay on the bottom of Lake Nemi.

Since the first century AD, and then throughout the Middle Ages, the legend circulated and was refreshed by the occasional discovery of strange finds by fishermen of the lake. 

The legend however had a grain of truth.

The Nemi Ships were two imperial Roman ships built by Emperor Caligula, sunk to the bottom of Lake Nemi, recovered in an archaeological mission conducted from 1928 to 1932. The recovery provided one of the most important contributions to the knowledge of Roman naval technique.

Thanks to some inscriptions it was possible to date the hulls to the time of Emperor Caligula (37-41 AD): the grandeur of the boats, the refinement of the decorations and furnishings have long led to think that the ships were elaborate floating palaces. Today the most accredited hypothesis is that they were ceremonial ships, intended for the celebration of religious festivals, in line with the sacred character of the place. 

The first hull measured 71 meters in length and 20 in width, the second 75 meters in length and 29 in width, and was characterized by the presence of long beams placed at regular distances, perhaps intended to bring outboard the oarlock. Two large anchors were also found: the first one, made of wood with a lead log of 5 m in length, is the only complete specimen of this type, known at the time. The second one, of the type called admiralty, was believed to have been designed by the English captain Rodger in 1851.

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An artistic representation of a Nemi Ship by CM Knight-Smith from an issue of Scientific American, c. 1906

Lake Nemi, of volcanic origin, is located about 30 kilometers south of Rome, on the Alban Hills. The area was inhabited since prehistoric times and in Roman times here stood the Temple of Diana Aricina, a religious and political center important and frequented.

The legend of the existence of two large ships submerged at the bottom of the lake, perhaps guardians of fabulous treasures, was handed down by the inhabitants of the place and was supported by random recoveries made by fishermen. From the Renaissance onwards, attempts were made to bring the ships to light: these attempts had dramatic consequences on the hulls, devastating the structures and removing artifacts and wood. As a matter of fact, the ships were too big and heavy to be fished out, but this will be realized only at the end of the 19th century.

Each ship contained a rotating statue platform. One platform was mounted on caged bronze balls and is the earliest example of the thrust ball bearing previously believed to have been first envisioned by Leonardo da Vinci but only developed much later”

Reconstruction of the Nemi Ship A


The first known attempt dates back to 1446, when cardinal Prospero Colonna, lord of Nemi, entrusted the recovery to the architect Leon Battista Alberti. The report of the enterprise is narrated by Flavio Biondo in his Italia illustrata: thanks to some expert Genoese swimmers, the closest ship to the shore was explored, determining its distance and depth; its recovery was attempted using a floating platform equipped with ropes and hooks.

In 1535, the Bolognese Francesco De Marchi carried out a series of dives, of which he gives an account in his work Della Architettura Militare. Using a special wooden bell with a glass porthole, which protects the upper part of the body leaving legs and arms free and allowing breathing, De Marchi determines the size of the hull closest to shore and its state of preservation.

Piston pumps (ctesibica machina) supplied the two ships with hot and cold running water via lead pipes”


After this attempt, the ships were basically forgotten for three centuries.

On September 10, 1827, the knight Annesio Fusconi, in front of a large audience, using a diving bell equipped with an air pump, reached the wreckage and took marbles, enamels, mosaics, fragments of metal columns, bricks, nails. 

However, not everything went as planned and many of the recovered artifacts were soon damaged or lost.

The recovered wood was used to make souvenirs. Bad weather interrupted the work, some of the rescued material was looted and Fusconi abandoned the mission. Later, he published the results of his work in a volume with the title “Memoria Archeologico-Idraulica sulla nave dell’Imperator Tiberio”, published in Rome in 1839.

Both ships had several hand-operated bilge pumps that worked like a modern bucket dredge, the oldest example of this type of bilge pump ever found”

Bronze beams heads
Bronze beams heads

The last operation before the intervention of the State was the one carried out by Eliseo Borghi in 1895, an intervention commissioned by the Orsini family and authorized by the Ministry of Public Education. Thanks to the work of a diver, a beautiful bronze ferrule of a rudder, worked in relief with a lion’s head, was brought to light. Tools and objects, bronze pillars, gilded copper tiles, mosaics, porphyry slabs, bricks but also spherical and cylindrical rollers were also brought to light, evidence of Roman technical knowledge, which leads to the hypothesis that ships had revolving platforms. Most of the recovered material was purchased by the National Roman Museum, while other discoveries took the road of the antiquities market.

As a result of Borghi’s work, the Ministry of Public Education imposed the cessation of attempts at salvage, which were progressively demolishing the hulls and, with the collaboration of the Ministry of the Navy, the phase of research began. The task was assigned to the engineer Vittorio Malfatti, Lieutenant Colonel of the Naval Engineers: during 1895 and 1896 Malfatti identified with certainty the position and the state of the two ships, carried out the general survey of the lake, and explored the accessible part of the emissary. He discarded the hypothesis of a direct lifting of the hulls, favoring the hypothesis of a lowering of the water level of the lake. 

On April 9, 1927, in a speech to the Royal Roman Society of National History, the Head of Government Benito Mussolini announced the decision to recover the submerged ships. Mussolini ordered Guido Ucelli to drain the lake and recover the ships. An ancient Roman underground water conduit linking the lake to farms outside the crater was reactivated avoiding the possible flooding of the temple of Diana. However, the tunnel collapsed at several points and was obstructed by materials. 

On June 15, 1928, two construction sites were set up: the first at the mouth of the drain, the second in Valle Ariccia. In four months, from June to October 1928, thanks to the employment of 70 workers organized in three shifts of eight hours each, the debris was removed, the tunnel was enlarged, the route was corrected and the pavement was leveled. On December 31, about 5 million cubic meters of water were extracted, half of what was needed for the emersion of the stern of the first ship.


In March a second pumping station was installed four meters lower than the first one and from April, because of the continuous landslides, the electric pumps were mounted on a floating pontoon, connected with flexible pipes to the rigid pipes placed on the shore. On March 28, 1929, the tallest structures of the first ship surfaced, immediately revealing the archaeological importance of the find.

Weapons, coins, decorations, tools, fish hooks, keys emerged; the position of each find was noted, and every detail was analyzed. On 7 September, after lowering the water level by twenty-two meters, the first ship emerged completely and at the end of January 1930, the second one emerged too. At the end of 1932, the second wreck was also recovered. At first, the ships are sheltered on the lakeshore, protected by wet tarpaulins that limit the drying of the wood and by an airship hangar.

Close-up of the pipes connecting the electric pumps mounted on a floating pontoon to the pipes located onshore

Between 1935 and 1936 the ships were exposed in the new Museum of Roman Ships, designed by the architect Vittorio Ballio Morpurgo. The museum was inaugurated on April 21, 1940.

The report of the recovery, the surveys, the investigations, the analyses were then published by Ucelli and other scholars in the volume Le Navi di Nemi, published in several editions by the Istituto Poligrafico e Zecca Dello Stato, starting in 1940. 


On the night between May 31 and June 1, 1944, a violent fire ravaged the museum, destroying the ships: only what had previously been brought to Rome was saved. Several shells of the United States Army hit the museum around 8 pm, causing little damage but forcing the German artillery to leave the area. Around two hours later, smoke was seen coming from the museum. 

To try to understand the causes of the fire, the government set up a commission that included architects, engineers, the fire brigade commander, and an artillery expert. The Commission ruled out that the fire had been caused by aviation bombs and artillery shells and concluded for the malicious origin, also considering the voluntary damage inflicted by German soldiers to the archaeological heritage of the museum and the failure to use the extinguishing systems Supplied.

Featured image: wikipedia
Sources: Wikipedia,


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