The magnificent Palace of Ardashir stands outside the ruins of ancient Gur, at a distance of about 2 km to the north. It was built on a remarkably vast scale, sometime later than Qal'e ye Dokhtar. Generally, it repeats the design of Qale ye Dokhtar but greatly exceeds it in size and quality. Although closely adherent to Parthian building techniques, Ardashir's Palace is the earliest embodiment of all the basic elements of Sasanid architecture which were to persist until the downfall of the empire, and would survive long afterward in the Islamic architecture of Iran.
Also, essentially influenced by the local methods practiced in Fars on a more modest scale in the preceding centuries, it has provided scholars with clues as to what the original residence of the local kings would have looked like. Ardashir's Palace has the most comprehensive plan and coherent composition. It is built next to a small, round lake fed with a spouting water spring. This spring brought into existence one of the lush oases so gratifying to the human spirit in arid lands. Cascading streams of water, a pond, and an orchard around it enhanced the elegance and distinction of the imposing palace. The pond was encircled by a wall with recesses for sitting, and the area in front of the benches was stone-paved. A staircase led from the lake to the entrance porch of the building. There was also a canal, and the excess water emptied into it. Today, this canal is filled up with masses of rubble stone, and the staircase and the wall around the lake have tumbled down.
However, the lake itself has survived, having withstood the effects of time better than the Sasanid structures or gardens. Together with the pond, the palace covers an area of more than 9,000 sq. m. The palace itself occupies a rectangle measuring 115 by 55 m and is divided into two nearly equal parts, of which one housed the reception section and the other contained the living quarters. The basic plan is undoubted to be recognized as a continuation of the principles of palace architecture developed under the Achaemenians. This principle involved the juxtaposition of two separate, but conjoined architectural complexes - the official, public palace, and the attached residential quarters. In Firuzabad, the reception area consists of a large entrance porch and three vast, domed halls in the center. The living quarters, lower in elevation, comprise a number of halls arranged symmetrically around an inner courtyard.
The entire building is constructed of rubble stone and fast-setting gypsum mortar of the highest quality, hand-mixed, and applied to form a layer 7 to 8 cm thick. The construction materials were undoubtedly those traditionally used in the area. Here and there, the mortar layer is pierced with holes to let out extra moisture and provide air circulation vents. Stones are laid in horizontal rows in successive vertical courses so that, in the event of an earthquake, only one of the courses would have sheared off. The walls of the building vary in thickness from 2.5 m in the courtyard to 5 m in the halls. The palace stands on a vast platform of stone plates laid on top of each other without mortar. This technique was an additional means of providing for the solidity of the building, which was created in a zone often threatened by natural disasters. On the outside, the palace was decorated with two rows of arched recesses, one just above the ground line, the other roughly coincident with the springing of the eivant vault. The lateral and back walls featured vertical recesses extending very nearly the full height of the building, with pilasters projecting from the wall face to separate them. The recesses evidently terminated in round arches similar to those of the blind arches that can still be seen on the fragments of the facade of the interior court. These projecting pilasters and false arches provided a chiaroscuro effect of light and shadow and reduced the monotony of the exterior walls. Very little remains of the interior decoration, but it seems that all the walls, as well as the inner surface of the dome, were covered with a coat of stucco, often carved or molded in beautiful patterns, and often polychromed.
The principal entrance to the palace is through a magnificent eivant overlooking the lake. Having a wide and lofty barrel vault, the porch measures 28 m long, 14 m wide, and 18 m high. Behind the central eivant runs a vestibule flanked by pairs of long, rectangular rooms oriented at right angles to it. Similarly designed, they are 10 m deep, and have barrel vaults with a span of 8 m. A recent archaeological survey has revealed that the porch was elevated some 1.5 m by later Sasanid kings to suit some purpose of their own. Coins from the late Sasanid period found at the site have further proven that the palace, or at least its reception area, were used by Ardashir's successors, and may have been modified to meet their needs.
The entrance section of Ardashir’s Palace did not have the fortifications characteristic of Qale-ye Dokhtar, and served the sole purpose of imparting additional magnificence to the building. The four lateral niches, two on either side of the central porch, were a bold attempt to develop and beautify the design employed in Qale-ye Dokhtar. On the east and west sides of the palace, there were two minor entrances used mainly for service purposes.
In Ardashir's Palace, the plan of Qal'e-ye Dokhtar is also enlarged by an inner courtyard, each side of which measures 28 m. This courtyard is accentuated by barrel-vaulted porches on its south and north, and is surrounded by a series of narrow, rectangular chambers, also covered with barrel vaults; these chambers served as private apartments. The staircase leading to the upper floor of the reception area is located in the northwest corner of the living quarters, to the right, as one enters the court. This section of the palace collapsed in the late Sasanid period. To safeguard it from further destruction, it was supported by stones and soil during the Buyid reign. At the same time, some rooms were added here to serve as a temporary abode for Buyid governors.