Seleucia on the Tigris was founded as a capital city by Seleucus I in 305 BC, and is now under a suburb in modern Baghdad. Tacitus described its big walls, and mentioned that it was, even under Parthian rule, a fully Hellenistic city. It was ruled by a senate of 300 people.
While relatively little of the city has been excavated, it must have been quite large, and appears to have incorporated both Greek and Mesopotamian architecture for the public buildings — just as finds have indicated an extensive non-Greek population.
Seleucia-on-Tigris was burned down by Trajan in 117 AD, relinquished by Hadrian the following year, then rebuilt in the Parthian style. It was finally destroyed in 164.
Seleucia in Syria functioned as the seaport of Antioch, and lay near the mouth of the Orontes. Paul and his companions sailed from this port on their first missionary journey (Acts 13:4). This city was built by Seleucus Nicator, the "king of Syria." It is said of him that "few princes have ever lived with so great a passion for the building of cities. He is reputed to have built in all nine Seleucias, sixteen Antiochs, and six Laodiceas." Seleucia became a city of great importance, and was made a "free city" by Pompey. It is now a small village called el-Kalusi.
Partly based on an article from the public domain Easton's Bible Dictionary, originally published in 1897. Please help the Wikipedia by bringing this article up to date.
There is a Seleucia in Turkey too, in the west of Mersin.