The ancient castle of Narin is a historical castle in Nain city, Isfahan province. One of the most important and oldest buildings in the city, "Narin Castle" or "Naranj Castle" can be related to the Parthian or Sassanian era, depending on the type of materials and the style of the building, and it was probably an ancient fire place. which has been used as an ancient fortress or old fortress of the city. There is no correct information about the function of the castle. But it is believed that this castle, together with the surrounding area, was the administrative and military center of the ancient city. Unfortunately, today nothing remains of this building except a few brick walls and the ancient remains of a huge castle.