Situated along the northeastern coast of the island, Ancient Kos emerged as a strategically positioned and culturally dynamic city within the Dodecanese, commanding maritime routes between Asia Minor and the Aegean region. Archaeological evidence indicates an organized city plan established in the fourth century BCE following the earthquake of circa 411 BCE and the subsequent unification of the island’s earlier poleis. The city was constructed on a rectilinear Hippodamian grid, characterized by colonnaded streets (cardines and decumani), public baths, temples, and port installations.

Excavations conducted since the Italian occupation in the early 20th century CE—most notably by Luigi Morricone and later Greek archaeological missions—have revealed a stratified urban sequence representing Classical, Hellenistic, Roman, and Byzantine phases. Among the most prominent remains are the Hellenistic agora, one of the largest in the Aegean, which functioned as the civic and commercial heart of the city; the Sanctuary of Heracles and the Altar of Dionysus; the Roman Odeon and gymnasium; and an extensive network of mosaicked houses reflecting elite domestic architecture.

The Asclepeion, situated approximately 3 kilometers southwest of the main city, functioned as both a healing sanctuary and a medical training center, affirming Kos’s association with Hippocrates and the development of rational medicine. The urban fabric, its harbor infrastructure, and monumental architecture collectively illustrate Kos’s integration into the Hellenistic koine and its later transformation under Roman administration.

Modern archaeological zones—particularly the Western Archaeological Zone, the Ancient Agora, and the harbor area—demonstrate the city’s continuity and adaptation across epochs. These remains, coupled with inscriptions, sculpture, and architectural fragments housed in the Archaeological Museum of Kos, provide a coherent material and spatial record of an Aegean polis that bridged Greek, Egyptian, and Anatolian cultural spheres.

circa 4000 BCE- Modern Period

Origins and Founding Myths
The island of Kos is enveloped in a rich tapestry of myth, legend, and early traditions that seek to explain its name, its first inhabitants, its sacred geography, and the divine or heroic figures associated with its foundation. These founding myths do not always align cleanly with archaeological or historical data, yet they have shaped Kos’s identity from antiquity.

One widespread legend holds that the eponymous founder‑king of the island was Merops (sometimes “Meropas”), from whom the name Meropian Kos is said to derive. Under this version, “Meropes” refers to the people of Merops or to his dynasty. The Homeric tradition also acknowledges Kos: in the Iliad, a contingent from Kos under Eurypylus participates in the Trojan War fought between ancient Troy and Greek States under Agamemnon.

Another myth locates Kos’s origins in divine genealogy. According to these tales, the gods Coeus and Phoebe (titans in Greek myth) are involved: Coeus is sometimes named as the first inhabitant, or progenitor of the line that includes Leto, mother of Apollo and Artemis. In some accounts Leto herself is said to have been born on Kos. These associations underscore the sanctity of the land in mythic memory.

The island’s name has several mythical explanations. One claims it comes from Koos, a daughter of King Meropas; another that it derives from a Titan named Kinnos, or from Koios. In some traditions Kos is named after Koos the queen’s daughter, while alternate etymologies suggest older roots in pre‑Greek or non‑Hellenic peoples—such as the Pelasgoi or Leleges—who are sometimes said to have been the island’s first settlers.

Myths also involve giants and battles between divine or heroic forces. One tradition holds that the island was once inhabited by giants, offspring of sky and earth. After being defeated in the struggle with the Olympian gods, some giants fled to Kos. One version says that Poseidon cut off a piece of the land and hurled it at the giant Polibotes during their struggle, thereby killing him. Other giants such as Koios, Phoebe, and Kinnos are said to have fled trauma or defeat to Kos.

The arrival of human settlers is also embedded in myth. Some narratives describe early colonists from Epidaurus—Dorians—settling the island. The Epidaurian settlers are sometimes linked with the introduction or development of the cult of Asclepius (Aesculapius), reflecting the later importance of the island’s medical sanctuary, the Asclepieion.

Heroic legends amplify Kos’s sacred landscape. Heracles (Hercules) is sometimes portrayed as having visited or stayed on Kos, or as a founding hero of sorts. The cult of Heracles on Kos features in ancient coins and local cultic practices: for example, coins from Kos display the head of Heracles, and his sanctuary was placed in a prominent location in the city. These tales connect the heroic age with the civic and religious life of Kos.

While these myths are ancient, they often served practical functions: legitimizing political institutions (by claiming descent from divine or heroic lineages), explaining the names of cities and places, endorsing sanctuaries, and giving moral or religious meaning to customs. Archaeology shows habitation on Kos from at least the Neolithic and Bronze Age (including Mycenaean period settlement at Serayia), and some of the mythic claims—early settlers, powerful visitors, cults to healing deities—correspond loosely with those long history elements.

Archaic Period
The early history of Kos remains only partially documented. During the Archaic Period it was a member of a religious-political amphictyonic league known as the Doric Hexapolis, which included Lindos, Kamiros, Ialysos, Knidos, and Halicarnassus. At the close of the sixth century BCE, the island came under the sway of the Achaemenid Empire. After the Greek victory at the Battle of Mycale in 479 BCE, Kos participated in a rebellion against Persian control. Archaeological evidence from this period indicates the presence of a small shrine dedicated to Hemera and Helios, reflecting cultic practices associated with day and sun deities.

Classical Era
Throughout the Greco-Persian conflicts, the rule of Kos alternated; on occasion it was governed by tyrants appointed by the Persians, yet much of the time it appears to have been under oligarchic rule. In the fifth century BCE, Kos became a member of the Delian League. Following Rhodes’ revolt, between 411 and 407 BCE it served as the principal Athenian station in the southeastern Aegean. In 366 BCE a democratic form of government was established, and the political centre of the island shifted from Astypalaea (situated at the island’s western extremity near what is today the village of Kefalos) to a newly established city, Cos, which was laid out according to the grid plan attributed to Hippodamus of Miletus. During the Social War (357-355 BCE), Kos aided in the weakening of Athenian influence; subsequently it briefly came under the dominion of Mausolus of Caria. Trade and cultural production flourished during this era. Proximity to eastern trading routes enabled the importation of silk thread; literary sources assert that women on Kos engaged in silk weaving. The presence of workshops, possibly staffed by female slaves, attests to a textile industry of some scale.

Hellenistic Period
In the period following the death of Alexander the Great, Kos was seized by Ptolemy I Soter from Antigonus I Monophthalmus, and was integrated into the Ptolemaic realm. Under Hellenistic rule, the island experienced its greatest prosperity. The Ptolemies valued Kos as a maritime stronghold in the Aegean, and the island became a provincial extension of the Alexandrian Museum in terms of learning and culture. Princes of the Ptolemaic dynasty often received part of their education here.

Kos was also renowned for its medical school, although the attribution of its foundation to Hippocrates during the Classical age remains unsupported by conclusive evidence. Among noted scholars resident there was the Hellenistic poet-scholar Philitas. Despite Ptolemaic sovereignty, Kos maintained a significant degree of political autonomy: decrees from the third century BCE indicate that local citizens’ assemblies and magistrates—such as the prostates and exegetes—presided over internal legislation and justice.

Economic prosperity during this era is visible in material remains: the Asclepeion was expanded; a theatre was constructed; markets with multiple stoas were built; there arose richly decorated houses and extensive fortification works. In 240 BCE, under guarantees from rulers such as Ziaelas of Bithynia, Seleucus II Callinicus, and Ptolemy III Euergetes, the Asclepeion of Kos was formally designated as an asylum—a status that increased its attraction to pilgrims and merchants.

Kos also developed a strong reputation for judicial fairness and arbitration. The city was regularly called upon to send judges to resolve disputes among other Greek cities. For instance, between 310 and 300 BCE, Kos arbitrated the conflict between Klazomenai and Teos; also it provided legal frameworks for the synoecism of Teos and Lebedus. Inscriptions show that in the following centuries its jurisdiction was sought in Naxos, Thasos, Erythrae, Mytilene, and Telos. In one recorded case at Telos, jurists from Kos resolved internal political crimes by allowing offenders to pay fines and make amends via public sacrifices and temple repairs.

Geographically strategic and well fortified, Kos played a prominent role in Aegean trade. It was famous for its wines. Under the Ptolemies and earlier, the city burgeoned into a major centre in the region. Ancient authors like Strabo and Diodorus Siculus describe the city as a strong port. There are traditions—quoted by Josephus through Strabo—that Cleopatra deposited gold there and that Mithridates I of the Bosporus was sent to retrieve it. Additionally, Herod (King of Judaea) is said to have provided funds for athletic prize-winners on Kos, and a statue was erected in honour of his son, Herod the Tetrarch. According to Christian scripture (Acts 21:1), Paul visited the island briefly.

Roman Period
During the Roman era, Kos generally enjoyed peace, interrupted only by occasional pirate raids and earthquakes. In 53 CE the island was granted the status of a free city, which conferred certain rights and privileges under Roman governance. A provincial library was established; several individuals contributed—among them Gaius Stertinius Xenophon, a Koan physician who served as doctor to emperors Tiberius, Claudius, and Nero, is known to have financed part of this institution.

Under Roman Imperial patronage, local institutions such as the gymnasiarch’s office received endowments from foreign rulers. An inscription dating to approximately 14 BCE honours Gaius Julius Herodes, who had adopted Roman naming conventions, possibly related to his contributions or financial support for such offices.

Byzantine Era
After the consolidation of Roman authority into the Eastern Roman sphere (Byzantine Empire), the Church became an important institution on Kos. Its bishopric was subordinate to the metropolitan see of Rhodes. Bishops from Kos took part in significant early ecumenical councils: Meliphron in the First Council of Nicaea (325 CE), Iulianus at the synod preceding Chalcedon (451 CE) as legate of Pope Leo I, Georgius in the Third Council of Constantinople (680-681 CE), and Constantinus attending the Photian Council of Constantinople in 879 CE.

Secular political details during this period are less fully documented. From the 8th to 9th centuries the island was administered by a droungarios, a Byzantine naval military office. In later centuries, particularly the 11th and 12th, Kos gained in strategic significance; Nikephoros Melissenos initiated his uprising there, and governance by a member of the Komnenos dynasty (Nikephoros Komnenos) is attested in the mid-12th century CE.

Kos remains today an ecclesiastical metropolis under the direct jurisdiction of the Patriarchate of Constantinople rather than the Church of Greece, and the Catholic Church lists it as a titular see.

Genoese and Hospitaller Periods
Following the 11th century CE, Kos experienced shifts in control, though it formally remained a Byzantine territory for a time. Genoese influence was asserted through a protectorate arrangement; from the 1320s it was nominally under Genoese rule (specifically under Vignolo de Vignoli), and the Knights Hospitaller were granted residence, with the island paying tribute to Genoa. During this era, Turkish corsair raids grew more frequent. Between 1391 and 1396 CE, Yıldırım Bayezid’s forces launched attacks; two towers added to the castle’s fortifications date from this period. In 1455 CE the Ottomans made a serious assault: Hamza Bey besieged and destroyed Andimacheia Castle. The final Hospitaller governor before Ottoman takeover was Piero de Ponte.

Ottoman, Italian, and Modern Era
Kos came under Ottoman control in the mid-15th century cE. It remained under Ottoman rule until the Italo-Turkish War of 1912 CE, when Italy seized the island. The Italians undertook significant building projects, especially after a devastating earthquake on 23 April 1933 CE. Architect Rodolfo Petracco drafted a new plan for the city; the old quarters were set aside as an archaeological park, while new sections were organized into residential, commercial, and administrative zones. During World War II, Kos was held by Italian forces until Italy’s surrender in 1943 CE; subsequently British and German troops fought for control in the Battle of Kos during the Dodecanese Campaign. After German occupation ended in 1945 cE, the United Kingdom administered the island until it was formally ceded to Greece in 1947 CE under the Paris Peace Treaty.

circa 400 BCE

The archaeological structures Ancient Kos preserves a rich array of structural remains that reveal its urban complexity, religious life, and public architecture from the Hellenistic through Roman and Late Antique periods. Prominent among these is the Agora, one of the largest ancient markets in the Greek world, laid out according to the Hippodamian grid after the synoecism of 366 BCE. The agora occupies sixteen building-insulae, has a central courtyard surrounded by stoas and shops, and is entered through three major gates (eastern, western, and northern), which led through arcades into the inner spaces. Many of its arcades, shop foundations, and colonnades are preserved, and it is flanked by temples and residential quarters.

Another key monument is the Harbour Quarter, which includes the Sanctuary of Aphrodite Pandemos and Aphrodite Pontia, twin Doric temples built on artificial embankments, surrounded by porticoes, and serving religious as well as maritime functions. With it are the Stoa of the harbour, the thermae (baths) associated with the port, and the Basilica and baptistery in the Christian era that in later centuries reused masonry from earlier structures.

The Asclepeion complex, located several kilometers south-west of the main city, is another significant site. It occupies multiple terraces, with shrines, a prophetic/hermetic medicine/sanctuary component (abaton), treatment rooms, and later Roman baths. Its highest terrace is dominated by a large Doric temple (second century BCE), while lower terraces include healing rooms and spiritual retreats. This structure not only testifies to Kos’s medical reputation in antiquity but also demonstrates integration of religious, therapeutic, and architectural design.

In addition, there are public works such as city fortifications walls, with towers and gates, which enclosed the residential quarters and controlled access to the port. These walls are circumscribed by complex construction phases; parts survive especially along the northern and coastal sectors, including stairways, towers, and sections of wall paralleling the shoreline.

Other structures include residential mansions (“Roman Houses” or Casa Romana) with multiple atria, luxurious floor mosaics, fresco decoration, and internal courtyards; the Roman Odeon for musical and theatrical performances; bath complexes (both in the Western Archaeological Zone and near the port) that indicate public bathing culture; and smaller shrines and altars, such as the Altar of Dionysus and the Temple of Hercules, often built on raised mounds or embankments, which accentuated their visibility and ritual prominence.