Imperial Superyachts on a Volcanic Lake
In a small volcanic crater lake 30 km south of Rome, Emperor Caligula constructed two of the largest and most technologically advanced ships of the ancient world in the 1st century AD. These were not warships or cargo vessels, but immense pleasure barges. The larger of the two measured 73 meters long and 24 meters wide, while the second was 70 meters long and 20 meters wide. They were floating palaces, complete with marble decorations, mosaic floors, heating, and complex plumbing systems that supplied hot and cold running water for baths and fountains.
The engineering of these vessels was far ahead of its time. Archaeologists discovered devices that would not be reinvented for over a thousand years. One of the finds was a thrust ball bearing, a mechanism made of caged bronze balls used to support a rotating platform, likely for a statue. This predates similar concepts by Leonardo da Vinci by nearly 1500 years. The ships also contained hand-operated bilge pumps, piston pumps for water, and anchors with a moveable stock design that was previously thought to be a much later invention. The hulls themselves were protected by a lead sheathing over tarred wool, a technique to prevent decay.
Draining a Lake, Losing a Treasure
For nearly two millennia, the ships lay intentionally sunk at the bottom of Lake Nemi. After several failed recovery attempts starting in the 15th century, an ambitious project began in 1928 under the direction of the Italian government. Rather than lifting the massive waterlogged hulls, engineers decided to partially drain the lake. They reactivated and cleared a 1.6-kilometer-long ancient Roman drainage tunnel, or emissarium, and used modern electric pumps to lower the water level. Between 1929 and 1932, the two ships slowly emerged from the mud.
The recovered hulls were moved into a massive, specially constructed museum on the lake's shore. For a little over a decade, the public could see these marvels of Roman engineering. The story ended in tragedy on the night of May 31, 1944, during World War II. A fire broke out in the museum and destroyed both ships, leaving only charred fragments and a few metal artifacts. The exact cause of the fire is still debated, with some accounts blaming retreating German soldiers and others suggesting an accidental consequence of Allied artillery fire. Today, the Museum of Roman Ships at Nemi shows scale models and the few artifacts that survived the blaze.