View from inside the Cave of Kynthos, place of worship of Heracles, on the sacred isle of Delos, showing an altar and a view of the ancient harbor. Delos, the birthplace of the twins Apollo and Artemis, was the mecca of the Greek world between the 7th and 1st centuries before the birth of Christ, visited by so many people in ancient times that the marble stairs in some places are worn to steep curves. The island, which became the first cosmopolitan center of Europe, drawing people of every nationality within sailing distance, later became a major center of trade. It has laid in ruins since it was sacked in 69 BCE.