Zibad Castle
Zibad Castle is one of the four historical monuments of Zibad, Iran, located in the Kakhk district of Gonabad County, in the Razavi Khorasan Province. It is believed to be the last refuge of Yazdegerd III, whose death signaled the collapse of the Sasanian Empire and the conquest of pre-Islamic Iran. In 2001, the castle was registered as a national heritage property. Zibad Castle has also been nationally registered under the name of Shahab Castle since 2002. Last shelter of the last Sasanian emperor. In 651, Yazdegerd III was defeated by the Muslim Arabs in the city  of Gonabad in the province of Merv. His heavy Sasanian cavalry was too sluggish and systematized to contain them; if he had employed lightly-armed Arab or East Iranian mercenaries from Khorasan and Transoxiana he would have been much more successful. Shortly after this, Yazdegerd III was murdered, leaving several different and contradictory narratives about his death. One source reports he sought refuge with a miller, who killed him to obtain his jewelry on the orders of Mahoe Suri. The narration of Al-Baladhuri in Kitab Futuh al-Buldan suggests that Yazdgerd was killed in Gonabad. The main text of  Blazeri's book "The Fate of Yazdgerd III": The death of Yazdegerd marked the end of the Sasanian Empire, the last Persian imperial dynasty before the arrival of Islam (224-651). All of Khorasan was soon conquered by the Arabs, who would use it as a base to attack Transoxiana. Sufeh Pir. Sufeh Pir is a cave believed to be the tomb of Piran Viseh in Kūh-Zibad mountain. He was a Turanian figure in Shahnameh, the national epic of Greater Iran. Beside Shahnameh, Piran is also mentioned in other sources such as Tabari and Tha'ālibī. He was the king  of Khotan and the spahbed of Afrasiab, the king of Turan. According to the book of Dr Abas Zamani Piran Viseh was buried in the cave of Sofe Zibad now called DarSufa Pir.