The Roof of the Taq-i-Kisra

Roof ot the Taq-i-Kisra

A higher resolution image, from a slightly different viewpoint

The roof of the Persian Throne Room of the Taq-i-Kisra, now in Iraq, is the best surviving example of an ancient large span structure built to a catenary profile, the shape that will minimise bending moments in a structure of uniform thickness, standing under its own weight.

The red line added to the photograph is a catenary, and the blue line a parabola with the same span at first floor level. The plot suggests that the roof shape from first floor level does indeed approximate a catenary, although the low resolution photograph and irregular outline of the end face of the structure make it difficult to be certain.

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7 Responses to The Roof of the Taq-i-Kisra

  1. Looks like a cantenary on the inside and a parabola on the outter surface. Looks a bit like a bit of thickening in the structure at the base of the arch


  2. Pingback: Elegant proofs 4 – The optimum shape of an arch « Newton Excel Bach, not (just) an Excel Blog

  3. Fisher says:

    You’re not likely to check this anytime soon, but if you do, could you please email me the link of the second picture untouched, or it itself
    its for a school add maths project


  4. dougaj4 says:

    Hi Fisher

    This is the link I used:

    Hope your project goes well.

    If you are working on arches you might be interested in this post as well:


  5. Fisher says:

    Thanks a lot, it’ll help a lot


  6. Sam says:


    Just a minor correction, Taq-i-Kisra is in Iraq not Iran although it was named after a Persian emperor.


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