In 1845–47 and again in 1849–51 Mr. (later Sir) A. H. Layard carried out a series of excavations among the ruins of the ancient city of Nineveh, "that great city, wherein are more than sixteen thousand persons that cannot discern between their right hand and their left; and also much cattle" (Jonah iv, II). Its ruins lie on the left or east bank of the Tigris, exactly opposite the town of Al-Mawsil, or Môsul, which was founded by the Sassanians and marks the site of Western Nineveh. At first Layard thought that these ruins were not those of Nineveh, which he placed at Nimrûd, about 20 miles downstream, but of one of the other cities that were builded by Asshur (see Gen. x, 11, 12). Thanks, however, to Christian, Roman and Muhammadan tradition, there is no room for doubt about it, and the site of Nineveh has always been known. The fortress which the Arabs built there in the seventh century was known as "Kal'at-Nînawî, i.e., "Nineveh Castle," for many centuries, and all the Arab geographers agree in saying that tile mounds opposite Môsul contain the ruins of the palaces and walls of Nineveh. And few of them fail to mention that close by them is "Tall Nabi Yûnis,"i.e., the Hill from which the Prophet Jonah preached repentance to the inhabitants of Nineveh, that "exceeding great city of three days' journey" (Jonah iii, 3). Local tradition also declares that the prophet was buried in the Hill, and his supposed tomb is shown there to this day.