In Greek mythology, the Arae were female spirits of curses, particularly of the curses placed by the dead upon those guilty of their death; they were associated with the underworld.
They are sometimes identified with the Erinyes.
In Roman religion, Arae is the plural for Ara, meaning altar. see: http://en.wikipedia.org/wiki/Glossary_of_ancient_Roman_religion text: ara The focal point of sacrifice was the altar (ara, plural arae). Most altars throughout the city of Rome and in the countryside would have been simple, open-air structures; they may have been located within a sacred precinct (templum), but often without an aedes housing a cult image. An altar that received food offerings might also be called a mensa, "table."
Perhaps the best-known Roman altar is the elaborate and Greek-influenced Ara Pacis, which has been called "the most representative work of Augustan art." Other major public altars included the Ara Maxima.