The first great development of ancient Persian architecture took place under the Achaemenid dynasty during the Persian Empire, from about 550 to 330 bc. Remains of Achaemenian architecture are numerous, the earliest being ruins at Pasargadae, the capital city of Cyrus the Great. These ruins include two palaces, a sacred precinct, a citadel, a tower, and the tomb of Cyrus. The palaces were set in walled gardens and contained central columnar halls, the largest of which was 37 m (111 ft) in length. The proportions of the principal rooms varied from square to rectangular; all were lighted by a clerestory. Walls were constructed of mud brick; foundations, doorways, columns, and dadoes along the walls were of stone. Columns were capped with stone blocks carved to represent the forequarters of horses or lions with horns, placed back to back. The roof was flat and was probably made of wood. The sacred precinct consisted of a walled court containing two altars and a rectangular stepped platform. The tower was a tall rectangular structure built of yellow limestone; a contrasting black limestone was used for the doorway and two tiers of blind windows. The tomb of Cyrus was a small gabled stone building placed on a stepped platform. The surrounding columns were placed there during recent Islamic times.
Darius I built a new capital at Persepolis, to which additions were made by Xerxes I and Artaxerxes I (reigned 465-425 bc). Three vast terraces were hewn and leveled out of the rocky site, and on them mud-brick and stone buildings, similar to those at Pasargadae, were erected. The buildings at Persepolis differed from those at Pasargadae in a number of ways. The columnar halls were square, walls were broken by windows and windowlike niches of stone, and the stone dado was not applied. Doorways bore a quarter-round cornice ornamented with a petal motif, probably of Egyptian origin. Column shafts were fluted rather than plain, the bases and caps were ornamented with floral decorations, and the termination of the column, called the impost block, took the form of naturalistically rendered forequarters of bulls or bulls with wings. These buildings had ceilings of cedarwood, carried on heavy balks or beams that rested on the stone impost blocks at the tops of the columns.
Other remains of Achaemenian architecture exist at Sūsa, where Darius I built a large palace, which was subsequently rebuilt by Artaxerxes II (reigned 409-358?bc). Royal architecture under the Achaemenids also included tombs cut in solid rock, of which the best-known examples are those at Naqshah Rostam near Persepolis. Little is known of the popular building practices of the period, but archaeologists believe that the ordinary dwelling was made of mud brick.
After the conquest of Persia by Alexander the Great in 331 bc, and the assumption of power by the Seleucid dynasty, Persian architecture followed the styles common to the Greek world (see Greek Art and Architecture). The great Greek-style Temple of Anāhita at Kangavar was excavated by the Archaeological Service of Iran with a view to eventual restoration. The temple had been destroyed by a severe earthquake in antiquity.
Subsequently, under the Parthian Arsacid dynasty, which lasted from about 250 bc to ad 224, a small number of buildings was constructed in native Persian style. The most notable monument of this period is a palace at Hatra (now Al Ḩadr, Iraq), dating from the 1st or 2nd century ad and exemplifying the use of the barrel vault on a grand scale. The vaults, heavy walls, and small rooms of this palace indicate a continuation of earlier Assyrian and Babylonian tradition