Location: 37.397N 25.264E

The quays are shown with dotted lines: nearly 200 m in the Sacred Port
and 800 m in the commercial port.
Delos was a famous island because of its central position in the Aegean Sea, halfway between Athens and Asia Minor. As the birthplace of Apollo, it was a holy place, and it was also a large emporium.
Thucydides (History of the Peloponnesian War, Book 3, Chap. 104, 426 BC) tells this story:
“The same winter the Athenians purified Delos, in compliance, it appears, with a certain oracle. It had been purified before by Pisistratus the tyrant; not indeed the whole island, but as much of it as could be seen from the temple. All of it was, however, now purified in the following way. All the sepulchres of those that had died in Delos were taken up, and for the future it was commanded that no one should be allowed either to die or to give birth to a child in the island; but that they should be carried over to Rheneia, which is so near to Delos that Polycrates, tyrant of Samos, having added Rheneia to his other island conquests during his period of naval ascendancy, dedicated it to the Delian Apollo by binding it to Delos with a chain.” (Translation, R. Crawley, 1903).
Plutarch tells a story also (Live of Nicias, Chap., around 420 BC):
“It is matter of record also how splendid and worthy of the god his lavish outlays at Delos were. The choirs which cities used to send thither to sing the praises of the god were wont to put in at the island in haphazard fashion. The throng of worshippers would meet them at the ship and bid them sing, not with the decorum due, but as they were hastily and tumultuously disembarking, and while they were actually donning their chaplets and vestments. But when Nicias conducted the festal embassy, he landed first on the neighbouring island of Rheneia, with his choir, sacrificial victims, and other equipment. Then, with the bridge of boats which he had brought along with him from Athens, where it had been made to measure and signally adorned with gildings and dyed stuffs and garlands and tapestries, he spanned during the night the strait between Rheneia and Delos, which is not wide. At break of day he led his festal procession in honour of the god, and his choir arrayed in lavish splendour and singing as it marched, across the bridge to land.” (Translation on Lacus Curtius, Loeb Classical Library, 1916).
Another story comes from Strabo (Geography, Book 14, Chap. 5, around 10 BC):
“The exportation of slaves induced them [pirates] most of all to engage in their evil business, since it proved most profitable; for not only were they easily captured, but the market, which was large and rich in property, was not extremely far away, I mean Delos, which could both admit and send away ten thousand slaves on the same day; whence arose the proverb, “Merchant, sail in, unload your ship, everything has been sold.” The cause of this was the fact that the Romans, having become rich after the destruction of Carthage and Corinth, used many slaves; and the pirates, seeing the easy profit therein, bloomed forth in great numbers, themselves not only going in quest of booty but also trafficking in slaves.” (Translation on Lacus Curtius, Loeb Classical Library, 1928).
The mass grave on Rheneia was found on the eastern coast at a place called Fossa Katharsis, but the exact location of Polycrates’ chain is not known. The location of Nicias’ floating bridge can be guessed from beach to beach, via the isle of Remmatia (ancient Hecate insula). The Sacred Port is located just in front of the Apollo temple and is now silted-up but still visible, and the commercial quays are disseminated along the coastline south of the Sacred Port, down to the Pointe des pilastres, and further south to the bay of Fourni where a natural shelter against northern winds (Meltem) is available.
Major archaeological excavations were conducted in the early 20th c. and most of the information available to us today comes from this period. The best recent source is from Hervé Duchêne and Philippe Fraisse, “Le Paysage portuaire de la Délos antique”, Ecole Française d’Athènes, 2001.
Some maps are provided hereunder.


(https://gallica.bnf.fr/ark:/12148/btv1b53061904m )
The Sacred Port

(https://www.planetware.com/greece/delos-gr-aeg-delos.htm)


The picture above was made before any archaeological excavation took place and is therefore not showing the modern breakwater which would be located in the centre of the bay. The ancient breakwater is located beyond the right side of the picture. The modern breakwaters just south of the Sacred Port and south of the Pointe des pilastres are the result of archaeological excavations which have dumped abundant rubble material into the sea at both of these locations, thus creating some protection of the coastline against northern wave attack.
The Sacred Port was initially probably no more than a protected beach area, but quays were gradually built. The oldest quay is dated to the 8th c. BC.

According to Ardaillon (1896) the large mole consisted of an existing reef reinforced by stones placed on top of it. However, no more than ca. 200 m can be considered as a breakwater, the northern end being more like a coastal protection running parallel to the shore.

This dump became the core of a modern breakwater structure with a quay on its southern side where today’s ferries bring tourists from Mykonos for day trips to Delos. It can be seen on the Google Earth picture below. This picture also shows a nice wave pattern due to a mild northern Meltem wind. Waves propagate mainly on the western side of both Remmatia islands and the Sacred Port is somewhat sheltered by the Lesser Remmatia islet (see detail picture below).

Lesser Remmatia islet and remains
of northern “large mole”.
It is interesting to see the wave diffraction pattern around the submerged breakwater remains.
These breakwater remains were surveyed by Philippe Fraisse at the end of the 20th c.
The breakwater portion shown on this picture is around 200 m long, including the curve inside the port. This structure is continued for another 80 m to the north as a coastal protection.
Unfortunately, no complete survey is available which would show the extend of the breakwater structure as it is today after 2000 years of wave action, but Duchêne & Fraisse (2001) mentions: “The large mole with a granite structure covering the Sacred Port and its southern end – the oldest part – with Cycladic polygonal ashlar”.

(Duchêne & Fraisse, 2001)
The Commercial Port
As shown on the overview picture above, the commercial port extends over around 800 m south of the Sacred Port. Shops and warehouses are aligned next to one another on the water side. They seem to have been literally on the water edge, like the old warehouses along the canals in Amsterdam.
Although some erosion occurred, the best-preserved remains are found at the Pointe des pilastres and south of it.

an archaeological dump of excavation rubble)

towards the remaining pilasters,
with the isle of Rheneia in the background.
Carlini’s Graffiti reproductions
We cannot visit the isle of Delos without speeking about ancient ships. A few of the famous reproductions made by Capt. Carlini are shown hereunder. The real graffiti are available in the beautiful Delos Museum, but almost nothing is now left of them.

If each sketched oar represents 3 levels of one oarsman, then this ship is a trireme with 170 oarsmen
(Musée de la Marine, Paris).

The graffito was over 1 m long and surely is one of the finest pictures of a trireme
(Musée de la Marine, Paris).
The Bull’s Monument
The Bull’s Monument takes its name from the statues of bulls, but has no further connection with these beasts. It was probably built around 330-320 BC by Athens and its dimensions are 69.4 x 10.4 m. It was a neorion hosting an ex-voto Athenian trireme of 35-40 x 5-6 m (L. Basch, 1989, “Le “navire invaincu à neuf rangées de rameurs” de Pausanias (1, 29.1) et le “monument des taureaux”, à Delos”).
The east side of the Bull’s monument, features a vast open space without any ancient construction, and Lucien Basch believes that this is the location of the “Delos ship”, which was the flagship of the Macedonian king Antigonus II Gonatas in the naval battle off Cos against Ptolemy II Philadelphus of Egypt, around 250 BC. The largest warships in antiquity were built In this period.
This mega-ship, named “Isthmia”, may have had 18 oarsmen per side, on two levels of 9 oarsmen, i.e. 36 oarsmen on a transversal section. With 50 similar sections, a total of 1800 oarsmen would have been on board. The ship would then have to be around 70 m long and possibly 20 m wide.
Lucien Basch suggests the graffiti below might have represented this ship. This is pure conjecture, but fascinating!

The graffito was 85 cm long and if each sketched oar represents 2 levels of 9 oarsmen, then this ship had 1800 oarsmen.
(Musée de la Marine, Paris).
Some believe that Caligula made a replica of this ship (ca. 40 AD) which is known as the “Nemi I” because it was used for naval games on Lake Nemi, north of Rome. This ship (and a second one) were found burried in the mud on the bottom of the lake, they were recovered and studied in 1927-32, but unfortunately disappeared during a fire in 1944 (G. Ucelli, “Le Navi di Nemi”, 1950).

Ship size 73 x 24 m, note the size of the persons standing in front of the ship.
According to Lucien Basch, this ship would fit perfectly in the open area east side of the Bull’s monument …