This work aims to study the trajectory of the architect Frei Otto (FO) using an exploratory analysis of his projects, which pays special attention to the conceptual and chronological temporal evolution, the type of structures designed, and the relationship with his partners for his built and unbuilt projects. In the latter case, the projects developed, not requested, that are not part of his built works have been approached (i.e., not considered under competition). The main results indicate that FO's architectural trajectory, from a chronological point of view, was intense, which is generally reflected throughout the years. The 1950s–1970s were very productive. In addition to the large number of projects, there were innovative designs for quantity and structural innovation in Germany and other countries (e.g., France and Saudi Arabia). The analyses that were carried out made it possible to ascertain FO's professional and academic influence, which has been reflected in his projects. Likewise, his relationships with his collaborators have been long-lasting in some cases. Practical Applications: This work aimed to study the work of the architect and engineer Frei Otto (FO), of recognized prestige by the awards received and his colleagues. Some mention the scarce diffusion of his work. The interest of this work lies mainly in making known to professionals, academics, and the general public, in a short format, such as that used in scientific papers, the design of his structures, built and unbuilt. As Félix Candela mentions about FO's career, he is a typical and outstanding example of architectural innovation who concentrated his vocation and efforts on the study and research of tensile structures. His international projection and toward the citizen, give Frei Otto academic interest. This work is developed from different perspectives, which include chronological, type of structure, the location and function of the project, and the collaborators he worked with, with whom he shared his innovation and construction activities. Attention has been paid to a collection of unpublished or little-known projects by FO. [ABSTRACT FROM AUTHOR]