Evolution of the Four-Ivan Plan in Iranian Architecture from the Achaemenid Era to the Qajar Dynasty

Abstract
The use of one or four iwans has long been a defining feature of Iranian architecture, appearing prominently in public, private, and governmental buildings. Among these, the four-iwan plan (Chahar-Eiwan) holds particular significance as a hallmark of Iranian architectural identity. This study adopts a descriptive-historical and analytical approach to examine the origins, evolution, and significance of the iwan in Iranian architecture. It addresses two central questions: 1) Why were the four-Iwan structures of the Achaemenid period, such as those at Pasargadae, designed with an extroverted layout? and 2) How did this architectural model influence the subsequent introverted four-iwan plans of the Parthian, Sasanian, and Islamic periods? The study hypothesizes that Achaemenid architecture, building upon Median traditions, sought to refine and monumentalize earlier forms. The extroverted design, characterized by four iwans opening onto garden spaces, reflects the centralized and hierarchical nature of the Achaemenid state and its emphasis on visual grandeur. In later periods, this model was adapted to new socio-political and spatial contexts, resulting in its transformation into more introverted configurations during the Parthian and Sasanian periods, which were further elaborated upon in Islamic architecture. Ultimately, the concept was revitalized in the Safavid and Zand periods, where it appeared in palatial, funerary, and ceremonial structures, blending Achaemenid spatial principles with Sasanian domed forms and culminating in its crystallization within the Isfahani style. The findings suggest that while iwans predate the Achaemenid era, it was during this period that the extroverted four-iwan plan achieved architectural coherence and symbolic meaning. This model was progressively internalized and reinterpreted across successive historical phases, underscoring the continuity and adaptability of Iranian architectural traditions.
Keywords: Four-Iwan Plan, Achaemenid Architecture, Extroversion, Safavid Architecture, Iranian Architectural Heritage.
 
Introduction
The iwan holds a special place in Iranian architecture so much so that Iranian architecture is often identified by the presence of this distinctive element. Since the Median and Achaemenid periods (the so-called “Persian style”), the iwan has gained increasing prominence and prestige in the history of Iranian architecture. While the significance of this architectural feature is widely acknowledged, key questions remain: In which regions of Iran did the iwan receive the most architectural attention? At what point did it begin to appear prominently in royal palaces and government buildings? And more fundamentally, how can the continuity of its use be meaningfully traced over time?
A preliminary hypothesis for the first question suggests that the use of iwans dates to the Iron Age, with more tangible examples visible at the archaeological site of Tepe Hasanlu in western Iran. It is plausible though not yet definitively proven that the earliest instances of iwans may have emerged as shaded porches in front of domestic dwellings in prehistoric village settlements. However, the question of where this innovation first occurred remains unresolved due to a lack of conclusive archaeological evidence. Based on current findings from archaeological excavations, it can be inferred that the iwan was particularly valued in regions where the climate varies dramatically throughout the year. In this regard, the mountainous zones of the central and northern Zagros appear to be especially significant. This inference is supported by the discovery of the oldest known iwan-bearing structures at Tepe Hasanlu IV (1200–800 BCE), located within this region. The importance of the iwan continued into the Median period, as evidenced at Tepe Nushijan, and was further developed during the Achaemenid era, where it was adopted in more formal and elaborate contexts.
The Medes and especially the Achaemenids utilized the iwan in a majestic and ceremonial manner. This raises an essential question: Did the iwans of Achaemenid palaces serve the same architectural role and function as those used during the Parthian, Sasanian, and Islamic periods? It seems likely that the role and symbolism of the iwan in Achaemenid architecture were preserved and gradually adapted in subsequent periods. The four-iwans in the pavilions and palaces of Cyrus the Great at Pasargadae were outward-facing (extroverted in form), integrated with surrounding gardens, and indicative of a deliberate relationship between architecture and landscape.
Although the Achaemenid iwan was influenced by earlier Median and Mannaean examples, it was executed in a distinct and more refined manner. The iwans of the Medes and Mannaeans were likely derived from vernacular residential architecture. The trajectory that began with the palaces of Pasargadae was eventually continued by the Safavids, notably in the Hasht Behesht Palace, where four outward-facing iwans were arranged around a garden in Bagh-e Bolbol and at Farahabad, Sari. Later, Nader Shah adopted the form in his mausoleum at Kalāt-e Naderi, followed by Karim Khan Zand in his tomb at Bagh-e Nazar, Shiraz, and finally, the Qajar era continued the tradition in much the same fashion.
Etymology and Definitions of the Iwan
Various definitions and descriptions of the term iwan have been presented in Persian dictionaries and lexicons. Some of these align closely with the focus of this study, while others reflect broader or differing meanings.
In Persian language, the word “Eyvān” (ایوان) [Iwan] refers to a terrace, portico, or open-fronted hall. According to the Mo’in Dictionary, an iwan is “a roofed part of a building with an open front, lacking doors and windows, and overlooking a courtyard. It can also refer to a palace or grand hall.”
Historically, iwans have been used since the Parthian era, and their construction has continued in various forms to the present day. Architecturally, an iwan typically consists of a barrel vault, enclosed on three sides and open to a central courtyard. They often function as transitional spaces entry or exit zones that allow air circulation while providing protection from direct sunlight. According to Kiani, the iwan has held exceptional architectural significance. Not only does it add grandeur and prominence to a building, but it also serves as a focal point for decorative elements, including muqarnas (stalactite vaulting), brickwork, stucco reliefs, and tilework. The iwan thus becomes a canvas for intricate artistry and ornamentation. Seyyed Sadr defines the iwan as a raised platform or hall in front of a room, enclosed on three sides and open to a courtyard through a wide, arched doorway. It is a roofed structure with a barrel vault, open at the front and devoid of doors or windows.
 
Varieties and Functional Aspects of the Iwan
The iwan, also referred to as pishan, is believed to have evolved from the giriyeh or summer iwan, typically constructed on the side or rear of buildings, facing away from direct sunlight. Architecturally, it also provided a suitable ground plan for performing prayer, as it was enclosed on three sides and open on one side. If an opening existed on the wall facing the qibla, it could easily be sealed, allowing a mihrab to be installed in its place. This functional adaptation can be observed in historical mosques such as those in Neyriz, Gonabad, and Ferdows.
In classical Persian sources, such as the Dehkhoda Dictionary, the iwan is defined generally as a portico or vaulted hall, and more specifically as a vaulted structure with a semicircular or niche-like shape often elevated and roofed located at the entrance of a palace or large residence. Terms like dar-gah (entrance hall) and ravaq (portico) are also used to describe similar spaces (Dehkhoda, s.v. “iwan”).
In certain traditional residential layouts, the iwan occupies the space in front of multiple rooms. Typically, one large room and a smaller adjacent room are connected by an iwan situated between them. This layout is observed in traditional houses in Lahijan. A similar form of iwan exists in rural areas of eastern Kurdistan, particularly in the villages of Qorveh, where the space between two rooms is referred to as an iwan. In contrast, the more monumental form discussed in this study is locally termed a bar-iwan (bārīwān) (see: Fig. 1).
 
Conclusion
The four-iwan plan became common in the palaces and pavilions of Pasargadae, and this stylistic approach was also applied in the Apadana Palace of Susa. While the four-iwan style continued into Parthian, Sasanian, and Islamic architecture taking on a more introverted form in contrast to the extroverted layout of Achaemenid structures it consistently reflected a symbolic four-part scheme. This design is deeply indebted to the ancient concept of the solar wheel or circle of life, a motif that lay at the heart of both architectural plans and ornamental programs across periods.
At the center of this enduring tradition is the iwan, a defining feature of Iranian architecture. The prominence of the four-iwan layout in successive historical eras owes much to the initial conceptualization and implementation by Achaemenid architects, who appear to have fulfilled the aspirations of their kings by integrating palatial structures with formal gardens. The placement of four iwans on each side of the building, opening onto the garden, reflects a conscious attempt to unify architecture with nature in a sacred and symbolic landscape. In ancient Iranian culture, including the Achaemenid era, the garden (pardis) was not only a symbol of beauty but also held religious and cosmological significance.
This architectural synthesis of palace and garden reached its zenith during the Islamic era, particularly under the Safavid dynasty, whose architects guided by royal patronage refined and emphasized this design principle. The most exemplary realization of this vision is found in the Hasht Behesht Palace, located in the Bagh-e Bolbol garden in Isfahan. Later, the Qajar dynasty also drew inspiration from this tradition. One of the key advantages of the four-iwan garden-palace layout was its ability to make full use of the surrounding garden from all sides, integrating nature and structure in a coherent and symbolically rich spatial narrative one where the garden itself tells its own story.