Discover Museum of the Roman Ships

The museum stands on the shore of Lake Nemi, and it was built for two ships that are no longer in it. Both were constructed under Caligula in the first century AD on this small lake; the larger was 73 m long with a beam of 24 m, the other 70 m by 20 m, and the larger was an elaborate floating palace with marble, mosaic floors, heating, plumbing and baths. They were raised from the lake bed in 1929 and destroyed by fire in 1944.

The museum is a functional building with a single argument: it is the size of its contents. Two halls were raised to take two hulls of 73 and 70 metres, which fixed the span, the height of the roof and the length of the frontage before anything else was decided, and the result reads from the outside as a pair of sheds rather than as a gallery.

That has an unintended consequence now. Because the ships burned in 1944 and the building did not, the architecture is the most complete surviving measurement of what it was built for -- a visitor standing in an empty hall is standing inside the dimensions of a ship.

Getting the ships out took five centuries of failure first. In 1446 Cardinal Prospero Colonna and Leon Battista Alberti found them at 18.3 metres, too deep to lift, and damaged them by tearing planks off with hooked ropes; Alberti learned little beyond the type of wood and that it was sheathed in lead. In 1535 Francesco De Marchi dived on a wreck in a diving helmet and brought up bricks, marble paving, bronze, copper, lead and timber, establishing that the hulls used mortise-and-tenon joinery. Objects were recovered and lost; there was no academic interest, so no research followed.

The lake was lowered to reach them. The ships were finally raised from the bed in 1929, and the museum was built on the shore to house what came up.

It burned on the night of 31 May 1944. Allied forces were pushing the retreating German army north through the Alban Hills towards Rome. On 28 May a German artillery unit set up a four-gun battery 150 metres from the museum and drove the custodians out, who hid in nearby caves. The German presence drew Allied counter-battery fire; several United States Army shells struck the building around 8pm, and significant flames were seen about two hours later. The Germans left on 3 June, and when the caretakers returned the ships were ash.

The official explanation stood for almost eighty years and was wrong. An Italian-American commission reported in July 1944 that the fire was "most likely" a deliberate act by German soldiers, and that account was widely accepted and recognised institutionally; the head of the German Kunstschutz office had argued at the time that American artillery was responsible. A 2023 study by Flavio Altamura and Stefano Paolucci reviewed the 1944 findings with unpublished documentation and modern fire-investigation methods, and concluded that the only plausible explanation is the Allied shells that holed the roof that same evening -- at least four explosive rounds aimed at a nearby German position struck the museum. The commission had excluded those impacts from consideration at the earliest stage, against the opinion of the only artillery expert among the investigators, who thought grenades were likely responsible.

Rebuilding has not finished. The Association Dianae Lacus was founded in 1995 and began Project Diana, a full-size replica of the first ship to deck level. Nemi's council voted funds for the forward section in July 1998; it was completed at Torre del Greco in 2001 and brought to the museum, with an estimated final cost of 7.2 million euro. Assimpresa announced sponsorship of all the timber in November 2003. No press release followed after 2004, and the association's website was deleted on 1 October 2011.

Is the museum open?

Not at the time of writing. The operator has posted an extraordinary closure running until 31 October 2026, so it is due to reopen on 1 November 2026. Check before travelling.

Are the ships still there?

No. They were destroyed by fire on the night of 31 May 1944. What survives is photographs, the survey drawings, original pieces recovered from the lake between 1895 and 1932, and the forward section of a replica brought here in 2001.

Who burned them?

The 1944 commission of inquiry said German soldiers, most likely deliberately, and that account was accepted for decades. A 2023 study by Flavio Altamura and Stefano Paolucci re-examined the original investigation with modern fire-investigation methods and concluded the only plausible cause was Allied artillery -- at least four shells aimed at a nearby German position struck the museum roof that evening, impacts the 1944 commission had excluded from the start.

Why build ships that size on a small lake?

Nobody knows, and the puzzle is sharper than it looks: the lake is 1.67 square kilometres and Roman law forbade any ship to sail on it because it was sacred, which implies a religious exemption. Caligula favoured the Egyptian Isis cult he had established in Rome and also supported that of Diana Nemorensis, whose temple stood by the lake.

How long does it take?

The operator puts the visit at an hour.

How do I get there?

The operator recommends the Via Appia to Genzano, then down to the lake by Via Diana.