In ancient times, Oropos was called Graia and was an important agricultural power belonging to the city of Tanagra. Graia, located where Skala Oropou is today, lay on the border of the administrative territory of the Boeotians and the Athenians. It was always a source of conflict between them, as it was a crucial port controlling the southern Euboean Gulf. However, following a victorious campaign by the Athenians against the Boeotians, Oropos came under Athenian control, and several years later it gained its autonomy.
During the Byzantine period, it emerged once again as an important agricultural power, as its fertile lands favored cultivation. However, during the Ottoman rule, it was largely destroyed and turned into a supply base for the Turks. Today, it has evolved into a modern town and a popular holiday destination for residents of Attica and beyond.

One of the most interesting places to visit is the Amphiareion, located in a small valley southwest of Skala Oropou, in Mavrodilesi. It was the largest sanctuary in ancient Greece dedicated to the chthonic god and hero of Argos, Amphiaraos, and served as the national sanctuary of Oropos.
The Amphiareion was founded in the late 5th century BC and was built on the banks of a stream. On the left bank stood the official buildings—the temple, the altar, the stoa, and the theater—while the residential area was on the right bank. In this area, alongside offices, shops, and guesthouses, there was the market and the Klepsydra, a unique hydraulic clock. The temple, dating back to the 4th century BC, measured 38 by 14 meters and was built in the Doric order.