These days, the ancient Iranian city of Rey has been reduced to a shadow of its former self. The ancient capital of the Seljuks — a Turkic dynasty that greatly contributed to the rich Turco-Iranian tradition — is now a suburb of the metropolis of Tehran. It is mostly associated with the Shah Abdol Azim shrine, one of the most venerated Shiite sanctuaries in the Tehran area. However, its other key landmark, Borj-e Tughrul (“Tower of Tughrul” in Persian), still stands strong.

Tughrul Beg, the founder of the Seljuk dynasty, declared independence from the Ghaznavids in 1037/1038 CE. Along with his brother Chaghri, he established control over Western Khorasan, northeastern modern-day Iran. Remembered as saving Nishapur from plunder, he established Rey as his capital in 1043. Tughrul led raiding bands as far as modern Iraq and effectively ended Buyid domination in Abbasid Baghdad, and was ultimately declared sultan of Baghdad by the Abbasid caliph. 

Today, Borj-e Tughrul, with its colossal shaft visible from afar, is situated in a garden surrounded by two-story buildings — most of them home to small businesses. Compared with other tomb towers of the period, "The architectural emphasis is on the mass, rather than decoration," according to Bernard O'Kane, an eminent professor of Islamic art and architecture. The strikingly massive monument, which is around 20 meters (65 feet) in height and has a diameter of 16.6 meters (54 feet), is still towering above Rey — and that is without its roof, which has been lost.

The tower is divided into 22 flanges on the outside — which some believe serve as a natural sun clock — and two doorways lead into the interior, a plain cylinder. The other feature that makes it stand out among its contemporaries is the use of a novel architectural technique: the transition of the outer stellar shape to an inner circle housing the dome. The Seljuks, "in the imaginative manipulation of brick masonry have no equals," wrote John Hoag, another eminent professor of Islamic architecture. Just by surviving to this day, with restorations under the Qajar era and also the Islamic Republic, the tower has proven its worth, said Ayse Atici Arayancan, an assistant professor specializing in Seljuk history at Hitit University in Ankara. "The only surviving monument from the Seljuk capital Rey is Borj-e Tughrul, which is important to shed light on the history, culture and the architecture of the period," Arayancan told Al-Monitor.