Jaabar castle is an Arabic structure, dating back to the beginning of 8-th century, but it has been something before it also.
The castle is now surrounded by the waters of Euphrates Dam, which was constructed by the help of Soviet Union in the 70-ies, and it was a great help to Syria's economy.
The castle has an entrance, less beautiful than in Najem Castle (also on Euphrates north to this), and has some walls remnants on the surface.
By the way Najem castle is far more impressive. Look for it in the blog.