Gonbad-e Qabus is one of the most extraordinary medieval buildings in Asia. The cylindrical brick tower rises 53 metres on a 15-metre artificial mound, tapers to a sharp conical roof, and is reinforced by ten triangular flanges that run from base to top. It was built in 1006 AD as a tomb for the Ziyarid prince Qabus, and it has been pulling visitors across the Turkmen steppe ever since — visible for tens of kilometres across the flat plain on a clear day.
The tower was inscribed as a UNESCO World Heritage Site in 2012. Engineers have studied it for what it tells about Persian brick architecture; the geometry of the flanges and the proportions of the conical cap are still cited as a masterclass in pre-modern structural design. There is a small park and modest interpretive centre at its base. Climb the hill, walk a slow circle around the tower, and notice how the angle of the flanges changes the silhouette as you move.