"The mosque holds a shrine which is said to contain the head of John the Baptist (Yahya), honored as a prophet by Muslims and Christians alike. The head was supposedly found during the excavations for the building of the mosque. "
"There are also many important landmarks within the mosque for the Shī‘ah, among them is the place where the head of Husayn (the grandson of Muhammad) was kept on display by Yazīd I. "
The place pictured above is "where all the other heads of those who fell in Karbalā were kept within the Mosque." (All history information from Wikipedia.)
At the shrines, I often noticed people weeping & praying.
I was very surprised to see this in the mosque because I don't know of any Muslim beliefs about baptism and, apparently, this was left over from when the Christians owned this property. I could understand John the Baptist's shrine since Muslims believe him to be an Islamic prophet as well as Jesus, Adam, Abraham, Ishmael, David and other Bible characters. But I was surprised to see the baptismal place. But I liked it.