These pictures were taken at the Mashad Al-Hussein, a Shi'a shrine since it holds the head (according to others it's in Medina instead) of Al-Hussein, son of Ali and grandson of the Prophet who was martyred at a battle at Kerbala. The date of his death, 10th of Muharram AD 680, is still remembered at the Shi'ite festival of Ashoura. Compare the mosque erected for his daughter, Say’yeda Roqayya, that is nearby.
Putting your head inside this rectangle enables one to touch what seems to be a silver plate that is probably the closest you can get to the grave.