It is the most known sanctuary of Amphiaraos,
a chthonic deity and hero. The Amphiarion is a very important site, due to the numerous inscriptions found, that belonged to the archive of the city.
They date to the 4th century BC.
Archaeological excavation at the site has been carried out by the Archaeological Society of Athens during 1884 - 1830.
The most important monuments of the site are:
The ancient sanctuary of hero Amphiaraos with the theatre,
and the temple.
The residential area with private houses, shops and offices.