Delos is a small island but its archaeological site is one of the most famous and most important of the world. I haven't been to another archaeological site with such easy access. As soon as you get off the ferry the site is almost right there. Some photographers may not like to have the ferries or yachts in the background of their photos. In a way it's interesting, like a sail into the legend and history.
According to the Greek mythology, Delos was the birthplace of Apollo and his twin sister Artemis. The Mycenaeans of that time were first to recognize the island as a place of worship. Many temples and shrines were built. Around 425 BC, the Athenians decreed a purification of the island. All graves were removed and it became law that no one would be allowed to die or be born on Apollo's island. The very pregnant women and seriouly ill patients had to move to another island to give birth or to die.
Let's hope in those old days there were no babies born prematured, or no Greeks would suddenly die of a heart attack or stroke on the holy island of Delos.