Ali ibn Musa (Arabic: علي ابن موسى ‎), also known by his title Ar-Ridha ("the contented"), was the eighth Shia Imam, after his father Musa al-Kadhim, and before his son Muhammad al-Jawad. He was an Imam of knowledge according to the Zaydi (Fiver) Shia school and Sufis. He lived in a period when Abbasid caliphs were facing many difficulties, the most important of which was Shia revolts. The Caliph Al-Mamun tried to fix this problem by appointing Al-Ridha as the next caliph, however, according to the Shia view, when Al-Ma'mun saw that the Imam gained even more popularity, he decided to correct his mistake by poisoning him. The Imam was buried in a village in Khorasan, which afterwards gained the name Mashhad, meaning the place of martyrdom. Today the Imam Reza shrine in Mashhad occupies a total area of 598,657 square meters (147.931 acres).