I think this came from Maths with Photographs, courtesy Richard Phillips in UK.
There is/was a free observation room located on the 27th floor.
Smallest floor is 45' per side.
Design allows more light to reach street.
Below. June 3, 1971, via SF Chronicle time vault: The Transamerica Pyramid is seen before the construction got to the apex in S.F.
The Home Page for the Transamerica Pyramid has/had detailed Facts and Information, nice drawings, including a Time-Lapse movie of its construction... found on TRANSAMERICA ONLINE.
Back to the Pyramids Home Page