Gonbad-e Qabus tower is a monument in city of Gonbad, Iran. It is built in 1006 AD and is also a UNESCO World Heritage Site since 2012.
The Tower in the central part of the city reaches 72 metres (236 ft), including the height of the platform.
The baked-brick-built tower is an enormous decagon building with a conic roof, which forms the golden ratio Phi, that equals 1.618.
The interiors contain the earliest examples of Muqarnas decorative styles. The decagon with its 3 meter-thick wall, divided into 10 sides, has a diameter of 17 m .
While it is not the world's tallest brick tower (it is shorter than the St. Martin's Church in Landshut, Germany and Church of Our Lady, Bruges in Bruges, Belgium and Qutb Minar in Delhi, India) but it is still the world's tallest pure-brick tower.