Examples of prehistoric and pre-Islamic architecture are found in ancient huts, remnants of old towns and villages, fortresses, temples and fi re temples, mausoleums and palaces, dams and bridges, bazaars, highways and roads, towers and outposts, garden pavilions, and monuments. The earliest forms of architecture known in Iran include peasant huts and farming hamlets. These structures were made of mud bricks and mortar and featured painted walls. From the fi fth millennium b.c. , handmade bricks instead of wood were used to make huts. One of the earliest examples of prehistoric architecture can be found at Zâgheh Tepe, a building complex from the late seventh and early sixth millennium b.c. , in the environs of what is now Qazvin. The Zâgheh Tepe, consisting of a fi replace, two storerooms, and a living room with decorated and red painted walls, was probably used for social and religious gatherings. Another prehistoric remnant of this period is Tepe Sialk, built in the late sixth or early fi fth millennium b.c. , near what is now the city of Kâshân. It is believed that the oval-shaped houses built from handmade sun-dried mud brick in this settlement represent the first rudimentary housing techniques used by humans at the time. Several other signifi cant excavated sites of this period are Tepe Hasan near Dâmghân, Tell-e Iblis near Kermân, and Tepe Hasanlu in western Azerbaijan. The last of these preserves the earliest structure in which wood was used as a supporting column. Between the thirteenth and eighth centuries b.c. , many wooden towers featuring entrance gates, paved courtyards, rooms, and nooks were constructed. Cone mosaics and colored and glazed bricks were used in huge ziggurats such as the marvelous fi ve-storied Chogâ Zanbil temple, constructed by the order of an Elamite king, on the bank of the Karkheh river ca. 1250 b.c. This monument had such an imposing dimension and superior quality of construction that its reconstructed remnants reflect a magnifi cent historical monument. A novelty in this structure is the construction of a portable water system used for both worshipers and the people of the city. Architecture during the time of the Medes, the first Iranian kingdom, established in the eighth century b.c. , was extremely well planned and constructed. Ecbatana, the capital of the Medes, was one of the earliest towns in Iran built based on planning and what can be considered at the time as urban principles. Another structure of importance in this period is the two-story royal palace of the Median kings at Ecbatana, surrounded by fortifi cations and towers. Stonecarving art found in later Achaemenid architecture seem to have its roots in this Median period. The Achaemenid period (ca. 550–330 b.c. ) offered the first great era and the richest collection of architectural works to the pre-Islamic Iranian history. Stretching from the Indus River in India to the Nile River in Egypt, from the Danube in Europe to central Asia, this vast empire produced huge gray and slender stone palaces, mausoleums, and fi re-temples, some of which have survived and are among the most attractive tourist sites in Iran and the neighboring countries. Persepolis, an impressive complex of palaces, was planned by Darius, not only as the seat of his government but also to showcase imperial receptions and festivals. Columns, reliefs, terraces, stone towers and pedestals, and pediments typifi ed the architecture in this period. Glazed bricks in blue, white, yellow, and green with animals and fl oral ornaments in palaces with large halls represented a somewhat new development in Iranian architecture and are indicative of a high-level of skill. The Achaemenids made full use of known technologies and the materials available in their environment. By using long Lebanese cedar beams instead of stone lintels, they achieved greater height with the fewer and thinner stone columns. The Pasargadae palace in Shiraz—built during the reign of Cyrus the Great (ca. 550–530 b.c .)—and majestic Persepolis, also near Shiraz and begun during the reign of Darius I (522–486 b.c .) , have come to represent the identity of pre-Islamic Persian architecture and even non-Islamic Iranian national identity. Persepolis is so vast and so rich that it took some 100 years to be completed. The Palace of Xerxes, the Palace of Darius I, the Treasury, the Hall of a Hundred Columns, the Apadana Palace (with a large terrace of 37 columns, each 72 feet high), and the Throne Hall of Xerxes are among the most majestic structures at Persepolis. The “Gate of All Nations” was the venue through which the representatives of different Iranian nations passed in order to reach the audience hall. The latter was completely destroyed by Alexander in 330 b.c. The magnifi cent Persepolis complex served successive Achaemenid kings a venue where vassal states would come for their annual tribute to the king during the celebration of the spring equinox. The tomb of Cyrus the Great, located in the south of Pasargadae, is a respected national shrine for many Iranians. It is a stepped platform surmounted by a peakroofed structure. The building used whitish limestone and was built by artists from Media, Egypt, and Lydia. Following the victory of Alexander the Great over the Persian army in 331 b.c. and the death of Darius III, the Iranian Empire came under Alexander’s control. In 330 b.c. , Alexander looted Persepolis and carried away many of its treasures. The Seleucids, who succeeded Alexander the Great, were very much under the influence of Hellenistic designs, and they mixed these designs with Iranian forms. Greek geometric designs were used in the construction of some cities and monuments. The Parthians (ca. 238 b.c. – a.d. 224) succeeded the Seleucids and gradually began to move away from Greek designs. Parthian architecture had several unique features, including prominent use of a formknown as ogee to Europeans, the emergence of the element of ayvân (an audience hall leading to a domed chamber), extensive use of cut stones and stucco for making walls and ceilings, and the common use of the vaulting technique with mud and fi red bricks. Parthian reliefs still exist at Bisotun and Susa. Also, the oldest known Iranian tower, Mil-e Ajdahâ, was constructed at what is now Nurâbâd in the Mamasani district of Fârs province during the Parthian period. At the time, this tower served as a guidepost for caravans traveling through the territories. Later, such towers became common as guideposts for cities, towns, caravanserais, and lighthouses in coastal areas. The Sasanids, who followed the Parthians, remained faithful to their Iranian predecessors and revived the earlier Achaemenid architectural glory. Unique features of the architecture of this era were the size of constructions in the form of large monuments and huge towns like Bishâpur, built by Shâpur I in Fârs; the advancement of stucco art used for palace decoration; the widest high-rising baked-brick vaults known at the time, such as the splendid Tâq-e Kesrâ palace at Ctesiphon in what is now Iraq; and the use of stone and gypsum as construction materials. Wall painting thrived during this period, and the artists not only decorated palaces and rock carvings but also arched dams. The Sasanids built elaborately decorated bridges and dams like the Shushtar dam on the Kârun River in Khuzestân. They also build numerous fortresses. In Sasanid arcitecture, domes, gates, fl oors, and walls were decorated with colorful mosaics. Master sculptors created beautiful stone-carved reliefs like Naqsh-e Rostam at Dârâbgerd (Fârs province) during the reign of Shâpur I. This monument depicts the victory of Shâpur I over the Roman emperor Valerian ( a.d. 260). Sasanid architectural influences persisted into the Islamic era and traveled far beyond the borders of Iran to India, China, Syria, Asia Minor, the Balkans, Egypt, and Spain.