The Gonbad-e Qabus is one of the earliest buildings of the Razi period and, more precisely, stands at the boundary between the Khorasani and Razi architectural styles. Among the important characteristics of this style are the use of stronger and finer materials, adherence to the principles of niyaresh (structural engineering), coursed brickwork on facades, geometric patterning of buildings with brick, muqarnas work, and above all the use of bricks of the highest possible quality. Professor Pope writes: At the foot of the eastern Alborz Mountains, facing the vast expanse of the Asian plains, a masterpiece of architecture rises — the Tower of Qabus, or the funerary tower of Qabus ibn Vushmgir. From its wide base to the top of its pointed roof, it measures approximately 51.95 meters, with about 10 meters underground. It was erected with extremely strong red bricks that have now taken on a hue of pewter and gold.
This colossal structure is among the oldest dated Islamic buildings and ranks among the greatest glories of fourth-century Hijri architecture. Located at the center of the city of Gonbad-e Kavus, atop a mound approximately 11 meters higher than the surrounding land, it was built in 397 AH (corresponding to 375 solar / 1006 CE) by the command of Shams al-Ma'ali Qabus ibn Vushmgir. Such tall buildings have always served a dual purpose: both as a landmark and guide for the city and as the burial site of their patron. In Iranian architecture, one encounters such buildings under the names mil (minaret), borj (tower), or gonbad (dome) along trade routes, built to mark the path of caravans and indicate the direction of cities, and there is no doubt that the Gonbad-e Qabus served this role as well, for it is clearly visible from great distances across the Turkmen Steppe. The Razi style is the fourth style of Iranian architecture. Although it originated in northern Iran, it took root in the city of Ray, where the finest buildings were constructed,
though they were lost in the wake of Mahmud of Ghazni's sacking of the city. In this style, buildings with diverse functions emerged — such as tower tombs and mils. In the Razi style, the construction of arches and domes advanced significantly, and varieties of pointed arches were employed for both arches and domes. Instead of the simple barrel vault (prevalent in the Khorasani style), four-part vaults, karbandi (ribbed vaults), kolonbu vaults, and four-centered vaults were used. Domes, too, were built by various methods in the Razi style. The discontinuous rak dome, built in northern Iran (such as the Gonbad-e Qabus), was also built in Ray and later in central Iran. Likewise, the first example of a discontinuous nar dome was built at the Kharaqan towers. Subsequently, more advanced versions were built in Shiraz in the tork-dar (ribbed) form.
This building consists of a minaret in the shape of a cylinder with a polygonal cross-section, featuring ten equal flanges (ribs or papils), each flange measuring five meters and forty centimeters in width, and each of the ten faces composed of three ribs, each rib two meters wide. The rooted bricks of the conical body have varying roots and bodies — that is, from bottom to top, the root length and the width and length of the body decrease in a specific ratio. On the southern side, there is an entrance, and within its pointed arch and portal, two rows of beautiful muqarnas work are visible. These muqarnas, despite their simplicity, are among the earliest examples of muqarnas work in post-Islamic Iran. The lofty conical dome of the building would have helped give this structure greater prominence as a symbol of the city and a caravanserai. The building, in its simplicity, is one of the most awe-inspiring structures known as funerary monuments.
Old photograph, 1913 solar (Archive of the Gonbad-e Qabus World Heritage Site). Building plan (photos from the World Heritage Inscription Dossier, 2010)
Excavation trench near the building's foundation and images of the foundation in various sections (photos from the World Heritage Inscription Dossier, 2010). Building body (Archive of the Gonbad-e Qabus World Heritage Site, 2018)
The building plan is circular with an internal diameter of 9.34 meters. Adding the wall thickness, the building's diameter reaches 14.89 meters, and including the papils, 17.33 meters. The Qabus tower has a brick foundation. In the most recent survey of the tower's base, an exact depth of 9 meters and 82 centimeters was measured. Furthermore, based on geotechnical studies, the foundation soil consists of fine-grained materials, and up to a depth of 4.5 meters it is fill soil, beyond which the natural ground begins. Therefore, the foundation of the Gonbad-e Qabus begins from firm ground and was built to a height of 9.82 meters using brick and materials identical to the building itself. The foundation diameter is 17.08 meters, and with a volume of approximately 2,200 cubic meters, it was built as a cylinder. In comparison with other historical monuments, it appears to be one of the most massive foundations ever executed. The building's floor is covered with large ordinary bricks, though this paving does not date to the time of construction, as the floor covering has been destroyed and rebuilt several times by excavators.
The building has a circular shaft with 10 triangular flanges rising to a height of 36.971 meters from the foundation level, placed at equal intervals. The spacing between the flanges is uniform from bottom to top, achieved by reducing the rib sizes at higher elevations. The spaces between the flanges are filled with brick, creating a solid and compact mass. The height of the building's body on the interior from the floor to the beginning of the dome is 35.266 meters, and on the exterior from the base to the base of the conical dome is 36.971 meters. Including the rooftop height, a total of 52.844 meters was recorded. The entire shaft is built with pale yellow bricks (red bricks that over time and with sun exposure have turned golden yellow) of excellent and dense quality. The building's entrance is located on the southeastern side. The entrance height is 5.565 meters on the outer wall and 4.328 meters inside the building; its width is 1.60 meters from the outside and 1.30 meters from the inside. The small dimensions of the doorway in comparison with the building's magnificent proportions serve to emphasize its height. At the pointed top of the entrance, there is a muqarnas throat that appears to be one of the earliest applications and developments of this type of ornamentation in Islamic Iranian architecture. The ten triangular buttresses (papils), outside the wall thickness, embrace the cylindrical wall. These buttresses serve the important function of neutralizing the dome's thrust force, which converts into a large overturning moment. The builders' artistry lay in presenting the buttresses as integral parts of the facade. Two rows of Kufic building-script inscriptions encircle the body like a belt, one row at eight meters from the base and the other higher up, beneath the conical dome.
These inscriptions are in simple (mu'allaqi) Kufic script, set within brick frames two meters long and eighty centimeters wide. The inscriptions begin from the southeastern face of the building, east of the entrance, and proceed clockwise from east to west. The starting direction of the inscriptions is the same as that of the western Radkan tower in Kordkuy. To make the inscriptions more legible or to conceal imperfections, the letters were coated with gypsum wash — although it was known that this coating would quickly deteriorate, the intention was at least to give the inscriptions a more finished appearance in the interim. These two inscription bands, identical in text and wording and repeated above and below, contain the patron's name, the date of construction, and the patron's purpose in building the structure. The complete translation of the inscriptions and their arrangement is as follows: In the name of God, the Compassionate. This is the lofty palace of Amir Shams al-Ma'ali, Amir son of Amir, Qabus ibn Vushmgir. He ordered its construction during his lifetime, in the year three hundred and ninety-seven lunar, and the year three hundred and seventy-five solar.
Above the flanged body, a conical dome rises to a height of 15.87 meters. The bricks used in the dome differ from those of the body. In constructing the conical roof surface, a type of wedge-shaped rooted brick was used, which prevented the roof from becoming pyramidal. The present cone, which is considered the tower's engineering masterpiece, has a smooth and uniform surface. In constructing this dome, special wedge-shaped bricks with tails were used — smaller bricks at the apex and larger ones at the base. The narrow ends of the bricks are fully embedded in the mortar, which has resulted in the bricks being very firmly secured in place. The use of the sloped rak covering in northern Iran was consistent with climatic requirements and helped preserve the building against heavy rainfall. The thickness of the roof covering, based on the geometric intersection of the inner and outer surfaces from the elevation point, was calculated at 103 centimeters. At a distance of 3.53 meters from the drip edge, on the eastern side of the roof, there is an opening measuring 2.13 meters in length and 1.85 meters in width that serves as a connection to the interior space. The form of this opening is open, narrow, and vertically elongated from bottom to top, placed for ventilation. The placement of the opening on the eastern side of the cone prevents rain and snow from entering the dome's interior. Light enters the dome's interior solely through this aperture.
Materials can be summarized in four types: brick, mortar, plaster, and pointing. Brick: All parts of the building were constructed entirely of brick, and the surface of the exterior bricks has been water-polished to a smooth finish. The clay of these bricks
Cross-section of the entrance. View of the entrance portal and the pointed arch of the dome (World Heritage Inscription Dossier, 2010). View of the stepped arch of the Gonbad-e Qabus (Archive of the Gonbad-e Qabus World Heritage Site, 2018). View of a flange or papil or buttress from the body of the Gonbad-e Qabus (Archive of the Gonbad-e Qabus World Heritage Site)
View of the inscriptions of the Gonbad-e Qabus (Archive of the Gonbad-e Qabus World Heritage Site, 2018)
is nearly uniform with very few voids. Moreover, gravel and sand particles are rarely visible in the bricks. Mortar: In constructing the body and dome covering, an extremely hard mortar was used that has bonded the bricks into a monolithic mass and has been responsible for the building's stability and endurance for over a millennium. Tests indicate that 90 to 100 percent of the mortar used in the building's construction was gypsum. Plaster: Tests conducted on the building's surfaces indicate a gypsum plaster in the applied mortar. Pointing of the building's walls: The tower's body has been pointed with extreme precision, with mortar joints measuring 2 to 3 to 4 centimeters. Throughout all the brick joints, the pointing has been carried out with the utmost refinement without any recessed gaps.
Geometric Proportions of the Plan, Elevation, and Section of the Qabus Tower. In the building's plan, the measurement of the thickest section — that is, the body and flange together — equals the height of an isosceles right triangle constructed upon the side of a regular pentagon inscribed in an inner circle with a diameter of 9.67 meters. Since the angles of the flanges are right angles, the ten right-angled corners visible in the building's plan can be defined by means of five squares inscribed in the outer circle with a diameter of 17.08 meters. The ratio of the tower body to the conical dome in the exterior form is two to one. The ratio of the inner circle diameter to the body height inside the tower is one to four. Here, the conical dome is decomposed into four equal triangles, and the egg-shaped roof is traced by three arcs on each side.
The construction of tower tombs in the land of Iran is observed in the post-Islamic era. The earliest tombs were four-sided and domed. But toward the end of the tenth century, the popularity of funerary towers prevailed. The preference for the tower over the four-sided building grew so strong that virtually all important types of funerary towers can be found in the period from approximately 1000 to 1200 CE. The majority of these tombs were built for amirs, generals, and rulers. Most of these buildings are of the finest brick, ornamented with various decorative brickwork patterns, often in the form of mounted spurs and inscription borders placed at the top of the door or beneath the dome, and sometimes corridors or throats add to their beauty. Multi-faceted or conical roofs are the standard covering of these buildings. In these buildings, the simplicity of the exterior facade and the emphasis upon
a single slender spire produces the tower's primary visual impact. Although the early towers stand only about 15 to 20 meters tall, they appear taller. Among these, buildings such as the Gonbad-e Qabus and the Toghrul Tower in Ray are genuinely tall structures, in which even the sense of height has been emphasized; the architect, by employing flanges as parallel, straight lines from base to the bottom of the dome, creates the illusion of a kind of upward thrust that makes the height appear greater than it actually is. The harmony of form and geometric order in this monument is noteworthy; the reason for its fine proportions is the use of elements such as rhythm, proportion, symmetry, and balance. Since the design and form available for tower tombs — particularly in medieval Iran — was limited to square or polygonal, circle or modified circle, and lateral expansion was precluded, the only subject of importance was therefore the height. Architects employed various methods, among which one can mention the creation of double-shell domes and tall, elongated cylinders in the body. In the late Khorasani style, buildings had already approached the Razi style, and they can be placed midway between the two: such as the Tomb of Amir Ismail Samani, the Tomb of Arslan Jadhib, and the Minaret of Ayaz. The influence of the Gonbad-e Qabus style is clearly evident in buildings such as the Mil-e Radkan in Golestan, the Lajim Tower in Mazandaran, and the Toghrul Tower in Ray. A comparison of the Gonbad-e Qabus with similar funerary tower tombs in the world demonstrates that the Gonbad-e Qabus is the oldest model of a rak-style funerary dome and, in terms of height and other architectural specifications, is unmatched. This building has been accepted as the fifteenth Iranian entry on the UNESCO World Heritage List.
The Use of Kufic Inscriptions and Their Place in Islamic Iranian Architecture. The presence of inscriptions in Islamic architecture is a prominent and important feature of every building. The inscription-based ornaments of Islamic architecture — including stucco work, brickwork, stonework, and tilework — sometimes used separately and sometimes in combination, have created beauty. The inscriptions of the Gonbad-e Qabus in Kufic building script (mu'allaqi) were first observed in the Razi architectural style during the Ziyarid period in the Gonbad-e Qabus, and despite their simplicity, they are fully legible and prominent. This script type is most manifest in buildings and architecture, and for this reason it was given the epithet "building Kufic." Kufic script, with its angular and straight lines, maintains
Samples of double-faced bricks and the method of surface attachment and Persian bonding of bricks (World Heritage Inscription Dossier, 2010)
Gonbad-e Qabus, design and architectural details of the dome covering (World Heritage Inscription Dossier, 2010). Geometric proportions of the building body (World Heritage Inscription Dossier, 2010)
Tables introducing towers across different periods and comparisons with the Gonbad-e Qabus (World Heritage Inscription Dossier, 2010)
Past restorations in various years (Archive of the Gonbad-e Qabus World Heritage Site)
its dignity and solidity at all times. The mu'allaqi script is rarely used in calligraphy, because the basis of this script is drawn on a grid. The mu'allaqi script was derived from the Kufic script for the purpose of adorning buildings, after the Kufic script itself. The brick inscriptions arranged in rectangular frames on the brick body of the Gonbad-e Qabus, repeated symmetrically above and below, are a prominent example of building Kufic and are similar to the inscription on the west side of the Radkan tower, which is likely contemporary with it. In the inscriptions of the Qabus tower, two types of dates were used: one in Hijri lunar and the other in the Yazdgerdi calendar.
Sound Resonance in the Design. The sound resonance focal point is not a historical feature of the structure; rather, it was accidentally identified and located in 1996 during a landscaping plan for the grounds. The collision of sound frequency at the station point (the white stone) with the prismatic section of the buttresses and the building's body creates sound reflection.
Restoration of the Building in Different Periods. The first extant restoration report was written by Nasrollah Meshkati, who himself carried out repairs and restoration of the building in 1938 and 1939. The dome had suffered considerable damage due to negligence; holes two to two-and-a-half meters deep had formed in certain sections of the base. The conical dome had sustained extensive damage on the eastern and western sides, and approximately 1,500 rooted bricks had been broken or dislodged by gunfire. The interior of the building also required repairs and corrections. In 1925, the base and platform of the building were repaired for the first time, and in 1931 it was registered on the National Monuments list. In 1937, the Russians excavated the center of the tower to a depth of 11 meters in search of the body of Qabus, finding that the tower's roots continued further still. From September 1939, restoration of the conical dome, repair of the inscriptions and the base platform, and interior corrections were completed. From 1939 to 1942, coinciding with the outbreak of World War II, a Russian customs house was established at the foot of the tower. In 1993, the Mazandaran Heritage Organization undertook the landscaping and improvement of the mound and grounds, with a plan incorporating ascending ramps, pedestrian pathways on the mound surface, paving, and the design of gardens and pools. In recent years, restoration operations have been carried out as follows: 2005 — emergency restoration of the rak dome; 2006 — stabilization of body bricks and pointing between bricks; 2007 — interior restoration for stabilization of body bricks and flooring; 2017 — most recent restoration completed.
References: World Heritage Inscription Dossier for the Funerary Tower of Gonbad-e Qabus, Tehran, 2010. Pirnia, Mohammad Karim (2008), Iranian Architecture, 1st ed., Soroush-e Danesh. Setayesh, Abdolmatin (2015), The Tower of Qabus, digital edition, Azad Publications, 1st ed. Saeedian, Abdolhossein (2000), Knowing Iran's Cities, 1st ed., Elm va Zendegi. Me'marian, Gholamhossein (2012), Niyaresh of Iranian Architecture, Vol. 1, 1st ed., Naghmeh-ye Noandish.
