The shrine of Sayyidna Ali.
South of Arsuf-Apollonia, on the western edge of Herzliya, at the top of a limestone hill overlooking the sea, stands a rectangular fortress-like building, commonly known as Mashad Sayyidna Ali. It is the burial site of al-Hasan ibn Ali, who was a descendant of the second Muslim Caliph Umar ibn al-Khattab.
According to Muslim tradition al-Hasan ibn Ali fell in battle in 1081 and the mosque was build in 1481.