The unknown and the famous were initiated into the sacred rites here, yet we know almost nothing about the Eleusinian Mysteries. What we do know is that the Mysteries commemorated the abduction of Demeter's daughter, Persephone, by the god of the underworld, Hades (Pluto). Demeter was able to strike a bargain with the god, who allowed Persephone to leave the underworld and rejoin her mother for 6 months each year. The Mysteries celebrated this -- and the cycle of growth, death, and rebirth of each year's crops.
Despite its substantial remains and glorious past -- this was already a religious site in Mycenaean times -- the sanctuary's present surroundings make it difficult to warm to the spot. Admittedly, there are the considerable remains of a Temple of Artemis, a 2nd-century-A.D. Roman Propylaea (monumental entrance), and triumphal arches dedicated to the Great Goddesses and to the emperor Hadrian. Hadrian's arch here, by the way, inspired the Arc de Triomphe on Paris's Champs-Elysées. Nearby is the Telesterion, the Temple of Demeter, where only initiates of the cult knew what happened at the sacred rites -- and they kept their silence.
One poignant spot is Kallichoron Well, where the goddess Demeter wept over the loss of her daughter, whom Hades (Pluto) spirited away. The dark god may have dragged Persephone with him through the cave here known as Ploutonion, which was believed to be an entrance to the underworld. It seems ironic that modern Elefsina itself is so ghastly that it has become something of a hell on earth. If you're in luck, the small museum (closed since the 1999 earthquake but open intermittently of late) will be open. It contains finds from the site, including several figures of Demeter and a lithe statue of Antinous, the beautiful boy who won the emperor Hadrian's heart.