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City Tower

Philadelphia, Pennsylvania, United States of America
1 of 4

Louis Kahn and Anne Tyng collaborated on the futuristic City Tower, designed for Philadelphia in the late 1950s but never built. It was, however, included in "Visionary Architecture," a 1960 exhibition at the Museum of Modern Art.


The City Tower is designed for city of Philadelphia. This city was the hometown of Louis Kahn. During the 1950s Kahn studied the city intensively. In a serie of designs he proposes major and monumental alterations of the city centre.

In the course of studying Philadelphia, Kahn starts to develop a new type of office tower. The base for this tower is a tetrahedron structure. Khan has always looked for 'a continuous structure worthy of being exposed' (paper 1944 Monumentality). He criticizes the Seagram building for the lack of a clear structural principle (CIAM Otterlo, 1959). In contrast, the City Tower is a form as pure result of a structure. A first model for the City Tower was developed (top right) to visualize this ideas.

However, already in earlier projects Kahn had stated that 'a tetrahedral concrete floor asks for a column of the same structure'. A second model was developed four years later. This model is a three dimensional structure growing upwards in a zigzag manner. A few vertical circulation cores run through the structure. The structure is made of precast concrete elements. The joints are overexaggerated, designed as plug-in structure. The joints ('Hollow Capitals') contain vertical staircases. The Hollow Capitals are quite important for Khan. In Perspecta 2 he discribes them:

'In Gothic times, architects built in solid stones. Now we can build with hollow stones. The spaces defined by the members of a structure are as important as the members. These spaces range in scale from the voids of an insulation panel, voids for air, lightning and heat to circulate, to spaces big enough to walk through and live in. The desire to express voids positively in the design of the structure is evidenced by the growing interest and work in the development of space frames'.The structure is the most striking element of the tower.Most publications just show the structure. It is important to notice that Kahn also studied the facade.

The proposal shows permanent scaffolding of aluminium louvres covering the entire interior. If realised the tower would not have been perceived as an open structure, rather as an multi-plane solid form, with an intensive play of light.


The City Tower Project is important as part of the broader development of spaceframes and the notion of growth. These frames enabled architects of the 1950s and 1960s to develop modular structures of utopian proportions. The impact of the structures on the organisation of space was huge.

Architects involved in this development of spaceframes, modular buildings and growing structures were among others Graham Bell, Richard Buckminster Fuller, Fumihiko Maki, Alice and Peter Smithson (Alison and Peter Smithson) and Reyner Banham.

Context of the City Tower

The City Tower project has a clear position in the development of ideas of Louis Khan and his assistant Anne Tyng. One of the themes visible throughout several projects of the late 1940s, 50s and 60s is the use of frameworks, clusters or cells to organize space. Other themes include growth, organicism, topology, structure and monumentality. The City Tower project features a structure which explores connectivity and growth at a monumental scale.

Many of the ideas for the City Tower originated in the Yale University Art Gallery (1951-1953) and other earlier projects. These projects all contain a frame, an organism with an integral, geometrical order. An important difference, developed by Anne Tyng, is the fact that the frame of the City Tower is occupied by human instead of mechanical installations. It becomes a habitable structure.

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  1. Analysis Made by David Strui
  2. University of Pennsylvania
lacuna, February 23rd, 2017
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