If you're looking to talk to the dead while visiting Greece, turn to the legend of Hades. The ancient God of the Underworld is associated with the Nekromanteion, the Oracle of the Dead, which visitors can still visit today though only ruins remain. In Ancient Greece, people visited the temple for ceremonies to communicate with the dead.
Like Zeus, Hades is usually represented as a vigorous bearded man. His symbols are the scepter and horn of plenty. He's also often depicted with the three-headed dog, Cerberus. Hades's strengths include his wealth of the earth, especially precious metals; persistence; and determinedness. His weaknesses include his passion for Persephone (also known as Kore), the daughter of Demeter and Zeus, and his own niece. (He kidnaps her to be his wife.) Hades is also impulsive and deceptive.
The most common origin story is that Hades was born to the Great Mother goddess Rhea and Kronos (Father Time) on the island of Crete, along with his brothers Zeus and Poseidon. Hades is married to Persephone, who must stay with him in the Underworld part of each year, and returns to the world of the living for the other part. His pets include Cerberus, a three-headed dog (in the "Harry Potter" movies, this beast was renamed "Fluffy"); black horses; black animals in general; and various other hounds.
Hades' Temples and Volcanos
Hades's temple is the spooky Nekromanteion on the River Styx along the west coast of mainland Greece near Parga, still visitable today. Hades was also associated with volcanic areas where there are steam vents and sulfurous vapors.
With permission from his brother Zeus, Hades sprang out of the earth and captured Zeus' daughter Persephone, dragging her off to be his queen in the Underworld. Persophone's mother, Demeter, who was unaware of Zeus' agreement with Hades, searched the earth for her daughter and stopped all food from growing until she was returned. Eventually, a deal was worked out where Persephone would remain one-third of the year with Hades, one-third of the year serving as a handmaiden to Zeus at Mount Olympus, and one-third with her mother. Other stories skip Zeus's portion and divide Persephone's time just between Hades and her mom.
Though a major god, Hades is Lord of the Underworld and is not considered to be one of the more celestial and bright Olympian gods, despite the fact that his brother Zeus is king over them all. All of his siblings are Olympians, but he is not. Interestingly, the concept of Hades might have had roots as the dark side of Zeus, pertaining to the king's duties in the Underworld, but he was eventually considered to be a separate deity completely. He is sometimes called Zeus of the Departed. His name loosely translates into "invisible" or "unseen," as the dead go away and are seen no more.
In Roman mythology, Hades' counterpart is Pluto, whose name comes from the Greek word plouton, which refers to the riches of the earth. As Lord of the Underworld, he was believed to know where all the precious gems and metals were hidden in the earth. This is why he can sometimes be depicted with the Horn of Plenty.
Hades can also be conflated with Serapis (also spelled Sarapis), a Greco-Egyptian deity who was worshipped alongside Isis at many temple sites in Greece. A statue of Serapis-as-Hades with Cerberus at his side was found at a temple in the ancient city of Gortyn on Crete and is in the Heraklion Archaeological Museum.