Rayen Castle (Persian: ارگ راين Arg-e Rāyen) is an adobe castle in Kerman province, Iran. The medieval mudbrick city of Rayen is similar to the Arg-é Bam. Rayen displays all the architectural elements of a deserted citadel. It appears extremely well preserved, considering the numerous natural disasters that have been destroying similar structures nearby, and it is one of the most interesting sites in Iran.

Arg-e Rayen was inhabited until 150 years ago and, although believed to be at least 1,000 years old, may in fact have foundations from the pre-Islamic Sassanid era.

The Sassanid (also Sassanian) dynasty was the name given to the kings of Persia, which includes much of present-day Iran. During the era of the second Persian Empire, from 224 until 651, the last Sassanid king, Yazdegerd III, lost a 14-year struggle to drive out the Umayyad Caliphate, the first of the Islamic empires. By the Sassanids, their Empire was called Iran or Eranshahr. The Sassanid era is considered to be one of the most important historical periods in Iran.
(from wikipedia)