The site of Nisibis, on the great military and commercial route between the Tigris and the Mediterranean, and commanding alike the mountain country to the north and the then fertile plain to the south, gave it an importance which began during the Assyrian period and continued under the Seleucidae (see Mesopotamia, vol. xvi. p. 48). From 149 b.c. to 14 a.d. Nisibis was the residence of the kings of Armenia, and it was there that Tigranes had his treasure-houses. The place afterwards figured frequently as a strong frontier fortress in the wars of the Romans and the Parthians, its brick walls being unusually thick and its citadel very strong. Ceded to the Parthians by Hadrian, it became a Roman colony (Septimia Colonia Nisibis) under Septimius Severus. It was heroically defended against Sapor II., who unsuccessfully besieged it thrice. In the peace made by Jovian, however, it passed into the hands of the Persians, who established a strong colony there. Nisibis early became the seat of a Jacobite bishop and of a Nestorian metropolitan, and under the Arabs (when it continued to flourish and became the centre of the district of Diyâr Rebi'a) the population of the town and neighbourhood was still mostly Christian, and included numerous monasteries. According to Ibn Haukal the taxes and dues derived from the town and district of Nisibin in 358 A.H. (969 a.d.) amounted to five million dirhems and 32,000 dinars. Arab geographers and travellers of the Middle Ages speak in high terms of the gardens of Nisibis, and the magnificent returns obtained by the agriculturist. According to Mukaddasi (oδ. 1024), acorns, preserved fruits, and manufactured articles such as carriages, inkstands, &c., were exported. A change for the worse soon afterwards set in. The town was so heavily burdened with taxes by the Hamdanid princes living at Mosul that the Arab tribe of the Bann Habib, although blood relations of the Hamdanids, migrated in a body into Byzantine territory, where they were well received, accepted Christianity, attracted other emigrants from Nisibis, and at last began to avenge themselves by yearly raids upon their old home. Ibn Haukal goes on to say that finally the Hamdanid Nasir ad-Daule took possession of the town, confiscated the estates of those who had emigrated, and compelled those who remained to substitute corn for their profitable fruit crops. This made a final end of the prosperity of Nisibis; the surrounding district, no longer protected against the incursions of nomad tribes, ceased to be cultivated and became the wilderness which it continues to be to this day.