Locally called Zindan-e Harun, this two story historical structure 12 km from the Tehran-Mashhad road at the foot of Mesgar Abad mountains, consists of a rectangular construction built with rough-hewn dark-colored stones and plaster mortar, and has a brick ceiling. Originally, it was nine meters high. There is an opening upon its southern wall from which you can go inside the building. Its construction has been attributed to the Buvayhids, 10th century AD.