By building taller, he said, he could gain the space he needs and still plan for such amenities as pedestrian passageways and improving the interplay of light and shade on city streets.

Toppling of Model Applauded

As Mr. Rouse made his presentation, illustrated with cardboard models, the tallest of the two tower models toppled. Its fall was greeted by scattered applause.

Word of the plans had already been reported, and it stirred opposition that was apparent from an informal phone- in poll conducted by The Philadelphia Daily News. Callers opposed breaking the height barrier by 3,809 to 1,822.

Though he is reserving comment until all aspects have been considered, Graham S. Finney, chairman of the Planning Commission, has observed, ''There is a feeling that those air rights up there are public spaces.''

'A Very Serious Proposal'

But the project is one that would be welcomed in many cities, he said, adding: ''We regard this as a very serious proposal. It marks a stage in the development of the city that cannot be taken lightly, and it indicates that we need to rethink our planning concepts.''

One concern voiced by planners is the continued eminence of City Hall itself and its position in the overall scheme of the city. It is now the city's physical focal point, and because of the way it was planned it is integrated into the life of the city and its citizens.

It was placed in the center of the city by Penn's surveyor, Thomas Holme, at the intersection of two arterial thoroughfares, Broad Street and Market Street.