Complex sentence: The Citadel stands on an artificial mound 130 ft. high, on a plateau across the Khasa River it is believed to be built by, the king Ashurnasirpal II, between 884 and 858 BC as a military defence line.
Split into simpler sentences: The citadel stands on an artificial mound 130 feet high located on a plateau across the Khasa River. It is believed to have been built by King Ashurnasirpal II between 884 and 858 BC as a military defence line.