Ancient Greek cities almost invariably had an "agora" and Roman cities adopted them as well.
In Athens, there are two surviving "agoras". The so-called Roman Agora is at the foot of the Acropolis, and includes extensive ruins. Alongside the archaeological site is the Agora Museum which is built to resemble an ancient Greek building.
The other agora in Athens is connected to the Roman Agora through the remains of a monumental gate, the Gate of Athena Archegetis. It is usally called the "Ancient Agora" and is located in the Plaka area, also near the Acropolis, and preserves ruins from a slightly earlier period in Athenian history.
The word "agora" is often combined with the Greek word for "fear", phobia, as part of the term "agoraphobic", and refers to the fear of being in crowds or in open spaces. While these seem contradictory, ancient agoras combined both. They were a very open area compared to the often-tiny streets leading into them, and they were also very crowded spaces at peak market periods.