Giant Ships of Rome

[Dardanus Lupus]

I was asked in another thread to open discussion about Roman "giant ships", such as vessels excavated from lake Nemi and now dated to AD 31-41 according to numismatic evidence.

These two enormous ships - a sailing ship and an oared galley - were built and anchored on lake Nemi. Remains of a temple was recovered from the second ship; they are now believed to have been connected with Isis worship. Lake Nemi was sacred to Diana (Diana Nemorensis), but from the time of Caligula there was also a prominent shrine of Isis.

Pillaged and deliberately sunk later in the first century (possible after Nero's fall?), they were recovered in a feat of engineering sponsored by Benito Mussolini in the 1930s, but destroyed during the second world war in 1944.

In 1999 Rosario D'Agata, former public relations director of an Italian petroleum company, established the Association Dianae Lacus to replicate Caligula's huge sailing ship - however, there has been significant delays. Reconstructed keel is now preserved in the empty museum built for these two ships.

Nemi ships were in my opinion one of the most important finds in terms of Roman maritime archeology. They were evidently built to highest standard and they did reveal several interesting and surprisingly advanced technical details:

- So-called "admiralty type anchors", first adopted in 1836-1852 in the British Navy
- Copper nails made of almost pure electrolytic copper. I would very much like to hear from a person acquainted with metallurgy, how this was achieved.
- Ball bearings. Possibly originating from a rotating platform?
- Piped water.

Another of Caligula's giant ships (a "mirabilis navis"), an obelisk carrier from Alexandria was deliberately sunk and filled with hydraulic cement in Ostia, as Suetonius tells us:

He formed the harbour at Ostia, by carrying out circular piers on the right and on the left, with a mole protecting, in deep water, the entrance of the port. To secure the foundation of this mole, he sunk the vessel in which the great obelisk had been brought from Egypt; and built upon piles a very lofty tower, in imitation of the Pharos at Alexandria, on which lights were burnt to direct mariners in the night. (Claud. 20.3)

The mole was excavated by O. Testaguzza, who did find remains of five ships, one of which was identified as the gigantic obelisk carrier (though estimates of its size vary).

To compare these behemoths of antiquity to later sailing ships, I made following table and diagram: