In 1990, UNESCO added Delos to the World Heritage List, citing its exceptional archaeological site which "conveys the image of a great cosmopolitan Mediterranean port", its influence on the development of Greek architecture, and its sacred importance throughout Ancient Greece.

Between 900 BC and 100 AD, Delos was a major cult centre, where the gods Dionysus and Leto, mother of the twin deities Apollo and Artemis, were revered.

The first took place in the sixth century BC, directed by the tyrant Pisistratus, who ordered that all graves within sight of the temple be dug up and the bodies moved to another nearby island.

In the fifth century BC, during the sixth year of the Peloponnesian War and under instruction from the Delphic Oracle, the entire island was purged of all dead bodies.

A new decree was eventually issued, so that no one should be allowed to be buried or give birth on the island due to its sacred importance, and to preserve its neutrality in commerce since no one could then claim ownership through inheritance.

Suda writes that the Greeks used the proverb "ᾌδεις ὥσπερ εἰς Δῆλον πλέων", meaning you sing as if sailing into Delos in reference to someone who is happy, light-hearted, and enjoying himself.

Evidence has been found of Roman baths, coins, an aqueduct, residential and elite houses, multiple churches, basilicas, and a monastery all from the first to sixth centuries AD, which, however, does not suggest that the island was continuously inhabited in the period.

Also, a number of wine presses were found amidst the ruins of the ancient city that date to this period, suggesting that the population at this time was engaged in considerable viticultural endeavour.