Rabbah in Smiths Bible Dictionary

(great). 1. A very strong place on the east of the Jordan, and the chief city of the Ammonites. In five passages -- De 3:11; 2Sa 12:26; 17:27; Jer 49:2; Eze 21:20 --it is styled at length Rabbath of the Ammonites, or the children of Ammon; but elsewhere, Jos 13:25; 2Sa 11:1; 12:27,29; 1Ch 20:1; Jer 49:3 simply Rabbah. When first named it is mentioned as containing the bed or sarcophagus of the giant Og. De 3:11 David sent Joab to besiege Rabbah. 2Sa 11:1,17 etc. Joab succeeded in capturing a portion of the place -- the "city of waters," that is, the lower town so called from its containing the perennial stream which rises in and still flows through it. The citadel still remained to be taken, but this was secured shortly after David's arrival. 2Sa 12:26-31 Long after, at the date of the invasion of Nebuchadnezzar, Jer 49:2,3 it had walls and palaces. It is named in such terms as to imply that it was of equal importance with Jerusalem. Eze 21:20 From Ptolemy Philadelphus (B.C. 285-247) it received the name of Philadelphia. It was one of the cities of the Decapolis, and became the seat of a Christian bishop. Its ruins, which are considerable are found at Ammon about 22 miles from the Jordan. It lies in a valley which is a branch, or perhaps the main course, of the Wady Zerka usually identified with the Jabbok. The public buildings are said to be Roman, except the citadel, which is described as of large square stones put together without cement, and which is probably more ancient than the rest. 2. A city of Judah named with Kirjath-jearim in Jos 15:60 only. No trace of its existence has yet been discovered.