The road 's construction was probably undertaken during the third Abbasid caliph al - Mahdi , father of fifth Abbasid caliph Harun al - Rashid , around 780 CE .
Head entity: al-mahdi Q293482 12 13 14
Tail entity: harun al-rashid Q131002 21 22 23 24
Relation (head \u2192 tail): P22
Inverse relation (tail \u2192 head): P40