The city walls of Yazd are one of the finest expressions of a vital tradition of military architecture in Central Iran, witnessed in varying scale from fortified villages, road outposts, provincial castles, imperial citadels to ramparts enclosing entire cities. A junction of both inter city and regional trade routes, Yazd has predictably been a fortified settlement since its inception in the Sassanid period. However, the larger military strategic importance of its geographical location within the Kavir region led to its successive building and expansion as one of Iran's most famed city fortifications. Built largely of mud brick and mud straw mixture reinforced with timber, the Yazd walls demonstrate a visual continuity in color, scale and form with the built fabric of the town. The Yazd city walls form a large part of the earliest known descriptions of the city, dating from the tenth century which describe a well-built, fortified city with iron gates, then known as Kathah. The walls, thus can be seen to not only have influenced the layout, orientation and expansion of urban built form but be intrinsically linked to the city's perceived and projected identity.
The city walls of Yazd have traditionally been the last shelter of threatened and eventually displaced Persian imperial dynasties. It was one of the last bastions to hold out against the Islamic, Seljuk, Mongol, Timurid, Safavid and Afghan invasions of Iran over the past millennium. Ala ud Daulah Kakoui of the Kakoui dynasty that replaced the Seljuks in 1033 is the first recorded constructor of the city's walls. The Fahadan and Seyed Golesorkh fortifications can be traced to the Kakoui period. However, the earliest existing portions of the wall and moat can be traced to constructions between 1346-47, in the Muzaffarid period as part of a larger urban design exercise to create a new imperial capital for the provinces Kerman, Fars and Shiraz. The contemporary fortifications of Shahzadeh Fazel and Kohneh castle lie in the urban area within the Muzaffarid walls, still known as shahr-e-koneh or old city. The siege and occupation of Yazd by Timur in 1393 brought about the single largest rebuilding of the city walls till date. In stark contrast to his reputation as a city pillager and destroyer, Timur exempted Yazd from taxes, undertook large urban building exercises and ordered portions of the city's southern wall to be entirely replaced, strengthened and extended with new barbicans. This strong machicolated wall, often over 15 meters high was only incrementally added to or repaired in the subsequent Safavid and Qajar periods. Large portions of the city walls encompassing the Shahr-e Nau or new city were demolished in the Pahlavi and present day Republican periods, to accommodate urban growth and expanding traffic routes.
More imposing and richer in architectonic qualities than the similar mud brick city walls of Bam, Yazd's walls were built before the active use of gunpowder in warfare. The influx of war technologies introduced by invading armies gave birth to circular, larger and more closely spaced barbican towers that allowed defenders to target the invader's vulnerable flank. Protected crenellations with arrow slits provided defensive positions while series of sluices allowed invaders to be discouraged by boiling oil or burning pitch. The walls were double layered with a high protective external curtain supported by a lower inner wall. The hollow space sandwiched between accommodated tiered firing galleries that allowed different firing angles and range for defending armies. Designed for defense against archers, catapults and other projectile attacks in long fought military sieges in medieval times, the walls proved ineffective and ironically harmful in nineteenth and twentieth century artillery battles. Lack of maintenance brought down what was not purposefully demolished to keep pace with changing methods of defense, transport and urban sanitation. Today, sections of the walls show eroded crenellations atop ramparts and deterioration of the lower base by water seepage and human activity caused corrosion.
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