In the Persian Empire Cissia（Κισσία) was a very fertile district of Susiana, on the Choaspes. According to Herodotus, the inhabitants, Cissii, were a 'wild', free people, resembling the Persians in their manners.
Herodotus and other ancient Greek writers sometimes referred to the region around Susa as "Cissia", a variant of the Kassite name. However, it is not clear if Kassites were actually living in that region so late.
Cissia (area) Wikipedia
In ancient times Cissia was subjugated by Tiglath-Pileser III.
At the time of the Persian Empire some Eretrians were settled in Cissia.
Once the Ionian Revolt was finally crushed by the Persian victory at the Battle of Lade, Darius began to plan to subjugate Greece. In 490 BC, he sent a naval task force under Datis and Artaphernes across the Aegean to subjugate the Cyclades, and then to make punitive attacks on Athens and Eretria. Reaching Euboea in mid-summer after a successful campaign in the Aegean, the Persians proceeded to put Eretria under siege. The siege lasted six days before a fifth column of Eretrian nobles betrayed the city to the Persians. The city was plundered, and the population enslaved on Darius's orders. The Eretrian prisoners were eventually taken to Persia and settled as colonists in Cissia.
Darius the Great, contrary to Eretrian expectations, treated them kindly, and gave them a village in the country of Cissia for their habitation, which was but a day's journey from Susa, where Apollonius of Tyana found some of their descendants 600 years afterwards.
Herodotus divided the Achaemenid Empire into 20 districts. According to him, Susa and the surrounding area, Cissia, paid 300 talents tribute.