It has been an honour to be invited to contribute to the Special Issue of the Journal of the IASS – International Assiciation of Shell and Spatial Structures. For this edition of the Journal, the editors gathered collaborators, friends and students of this outstanding personality. The works of Frei Otto and his teams are still today a source of inspiration for various disciplines, ranging from architecture and engineering to the arts and to socio-cultural aspects.

In my contribution, I give an overview of Otto’s approach to evaluate comparable structural systems, then leading to the methods of topology optimization, which give the opportunity to both design and evaluate structural geometries.