The Palace of Ardashir Pāpakan (in Persian: دژ اردشیر پاپکان Dezh-e Ardashir Pāpakān), also known as the Atash-kadeh آتشکده, is a castle located on the slopes of the mountain on which Dezh Dokhtar is situated on. Built in AD 224 by King Ardashir I of the Sassanian Empire, it is located two kilometers (1.2 miles) north of the ancient city of Gor, i.e. the old city of Piruz-Apad in Pars, in ancient Persia (Iran).
The structure contains three domes, among other features, making it slightly larger and more magnificent than its predecessor, the nearby castle of Dezh Dokhtar. However, it seems that the compound was designed to display the royalty image of Ardashir I, rather than being a fortified structure for defense purposes. That is why perhaps it would be best to refer to the structure as a "palace" rather than a "castle", even though it has huge walls on the perimeters (twice as thick as Ghal'eh Dokhtar), and is a contained structure. From the architectural design, it seems the palace was more of a place of social gathering where guests would be introduced to the imperial throne.
What is particularly interesting about this palace is that its architectural design does not exactly fall into that of the Parthians or even Sassanian category; the design is a unique design particular to architects of Fars.