The Feast of Sacrifice is based on the experiences of the Prophet Abraham. All three monotheistic faiths believe that he was tested by God, who ordered him to sacrifice his son before replacing him with a ram at the last moment.
Muslim Caliphs almost always wanted to keep the holy relics of Prophet Mohammed close to where they ruled. In the end, the Ottoman rulers brought them to Istanbul, where the Turkish government safeguards them in the historic Topkapi Palace.