There is a flyblown, wind-tossed, overpriced canteen. Avoid it if you can.
As I mentioned above, you'll be better off carrying your own food and water to this open-air museum.
According to mythology, Delos was the birth-place of Apollo and Artemis. Leto was said to have given birth to the divine twins, Apollo and Artemis by the Sacred Lake, in the northeast part of the site. (This lake was drained in 1925 to prevent the breeding of malaria-carrying mosquitoes.)
The first signs of habitation on the island date from the 3rd millenium B.C., and important remains of the Mycenaean period have been uncovered in the area of the sanctuary.
A festival in honor of Apollo was established during the 8th century BC and many temples and shrines devoted to him. By the 7th century BC Delos had become the religious and commercial center of the Amphictionic League. In 478 BC it came under Athenian power with the establishment of the Delian League, which decreed that no one could be born or die on this tiny island, thus diminishing the local native population. Later the natives were banished to Achaia in the Peloponnese.
Delos was a major religious center as well as commercial center during Hellenistic times, with traders from Egypt and Syria who built temples to their own deities (though Apollo was the central deity worshipped here). The Romans made it a free port (i.e., an international harbor) during the second century BC. There was a flourishing slave trade with 10,000 humans sold daily.
The declaration of Delos as an "international" harbour by the Romans led to an influx of foreigners who became a significant element of the island's population. By the 2nd and 3rd centuries A.D. only a small settlement existed on Delos and, as Christianity gradually replaced the ancient religion, the island finally lost its importance.