Arq of Tous, or according to people, "Place of Mamoun", is now a high and vast clay hill, located 300 m in the South of the Tomb of Ferdowsi.

In its inhabited days, "Old Castle" (Kohan Dezh) and "Arq of Tous" were placed there and palaces were constructed upon it.

Kohan Dezh, the heart of the city, was separated by the still recognizable fence and moat.

The remains of the walls, still observed on Arq ruins, belonged to Timurid era and the end of habitation of Tous, which were founded on the ruins of former palaces.