According to 'Jamiut Tawarikh' (p. 122), the construction of the fortress of Maimundiz began in 490/1097, but Kashani (d. 738/1338) determines in 497/1103 in his 'Zubdat al-Tawarikh' (p. 144). Juvaini (2nd vol., p. 627) however writes that it had been built in the time of Alauddin Muhammad. It seems that the location had been selected earlier, where a small fortress was built, known as Maimundiz. In the time of Alauddin Muhammad, the site had been freshly chosen and projected for a stronghold. His officers and ministers had surveyed the heights and summits of the mountains during 12 years until they chose a lofty peak, and built there a castle, and provided it with ample supply of water.
The site of Maimundiz, located to the north of presently village of Shams Kilaya and westward from Alamut. Because of the great altitude, the cold was so extreme as to make it impossible for beasts to find a home or live in that location from the beginning of autumn until the middle of spring. The family of Alauddin Muhammad and his attendants were shifted from Alamut to Maimundiz.
The site of Maimundiz was identified in 1960 by an expeditionary party organised at Oxford University for exploring the Ismaili castles of northern Iran, vide 'The Castles of the Assassins' (London, 1963) by Peter Willey. Dr. M. Sutude in 'Qila-i Ismailiyya' (Tehran, 1966, pp. 108-122), who is well grounded with the geographical area, rejected the identification of Maimundiz made by Peter Willey's expedition.
Shamsuddin bin Ahmad al-Tayyibi (592-652/1195-1254) was an eminent Ismaili poet in Syria. He travelled excessively in Iran and visited Alamut during the period of Alauddin Muhammad, where he served as a court-poet. His poetical works are not accessible. He left Alamut most probably after the death of Alauddin Muhammad, and returned to Syria, where he died.
Alauddin Muhammad's rule was long and prosperous. It was a period of both intellectual and political activity. The glory of his rule was the patronage of science and learning, attracted a bulk of scholars from outside. He was fond of shepherding and used to visit the villages to help the people in their dairy products, and the cattle breedings. His old enemies conspired through his close advisor, Hasan Mazandaran, who killed the Imam on 29th Shawal, 653/December 1, 1255. His body was found at midnight in a wooden hut, near his sheep-fold in the village of Shirkuh in the western part of the district of Alamut. Alauddin Muhammad had many son's whose detail is not accessible. It is however known from Juvaini that Shahanshah, Shiranshah and Iranshah were his sons, and the elder one was Ruknuddin Khurshah, who was consigned the office of Imamate.