Ungers' buildings are characterized by strict geometricaldesign grid. Basic design elements of his architecture are elementary forms such as square, circle or cube and sphere, which Ungers varied and transformed in his designs. As an architectural theorist and university lecturer, Ungers developed what his critics called "quadratism", his admirers "German rationalism". In doing so, he resorted to the teaching of Jean-Nicolas-Louis Durand who had published in 1820 his pattern books with geometric prototypes for "any building". In his formal language, Ungers explicitly referred to elementary architectural design elements that are independent of contemporary tastes. His historical role models in the history of architecture come mainly from Roman-Greek antiquity. His work was therefore occasionally criticized as formalistic. In connection with his construction on the Frankfurt Messe grounds, there was often talk of a "new clarity". Like hardly any other architect, Ungers has remained true to his once chosen formal language for decades. He was one of the leading theoreticians of Second Modernism. Well-known students of Ungers include Max Dudler, Jo. Franzke, Hans Kollhoff, Rem Koolhaas, Christoph Mäckler, Jürgen Sawade and Eun Young Yi.
Ungers Archive for Architectural Research contains his architecture library, which he began building in the 1950s, as well as the architect's entire artistic legacy. The library focuses on architecture tractate, works on the emergence and further development of perspective and publications on theory of colour. The library includes the first edition of Vitruv's De Architectura Libri Decem of 1495 as well as rare editions such as the Staatliche Bauhaus in Weimar 1919-1923 and publications of the Russian avantgarde, for example Von zwei Quadraten by the architect El Lissitzky. Together with his estate it is housed in the library cube of Ungers' listed building in Belvederestraße 60, Müngersdorf and is available to the scientific public for research purposes.
Ungers' collection of architectural icons
Part of the Ungers Archive for architectural Research are the models of historical architectural icons which the diploma designer and architectural model builderBernd Grimm built in collaboration with the architect. Ungers goal was to create a "three-dimensional collection" of historically significant buildings. The models are made of white Alabaster gypsum and have a wooden substructure.
2006 Entrance to the ruins of a Roman bath in Trier
;Proposed or under construction
In 2000, he won an architectural competition to redesign the Pergamon Museum in Berlin. His controversial plan proposes large alterations to the building complex which has remained unchanged since 1930. The rebuilding is scheduled to end in 2022.
Writings
Entwerfen mit Vorstellungsbildern, Metaphern und Analogien. Anmerkungen zu einem morphologischen Konzept, in: Architektur 1951-1990, Stuttgart, 1991
Morphologie. City Metaphors, König, 1982
Die Thematisierung der Architektur, 1983, published by Technische Universität Dortmund and Walter A.Noebel, Niggli Verlag, 2009,