An agora was an essential part of an ancient Greek polis or city-state. An agora acted as a marketplace and a place of congregation for the citizens of the polis. They arose along with the poleis after the fall of Mycenaean civilization, and were well established as a part of a city by the time of Homer (probably the 8th century BC).
The most well-known agora is in Athens. The agora in Athens also had private housing, until it was reorganized by Pisistratus in the 6th century BC. Although he may have lived on the agora himself, he removed the other houses, closed wells, and made it the centre of Athenian government. He also built a drainage system, fountains, and a temple to the Olympian gods. Cimon later improved the agora by constructing new buildings and planting trees. In the 5th century BC there were temples constructed to Hephaestos, Zeus, and Apollo. The Areopagus and Boule met elsewhere in Athens, but the largest public meetings, such as those to discuss ostracism, were held in the agora. The law courts were located there, and any citizen who happened to be in the agora when a case was being heard could be forced to serve as a juror; the "Scythian archers," a kind of mercenary police force, often wandered the agora specifically looking for jurors.
The agora in Athens again became a residential area during Roman and Byzantine times.