A recent post at the ifoApplestore blog explores the careful considerations of design at Apple's retail stores, including the sidewalk elements.
Blogger Gary Allen said that what appears to be a simple storefront is a carefully designed piece of architecture, where the "new sidewalk, store window panels and inside stone floor tiles all are dimensioned and positioned to present a symmetrical appearance."
In this case, the master element is the stone floor tiles, which are 76 centimeters square (about 30 inches). The glass window panes are then manufactured to a multiple of that dimension.
There's a drawing on the site that shows the various elements and their relationships of the new 4th Street store in Berkeley.
I was once told a tale about the design of the first Apple Store back in 2001. A full-sized mockup of the store was built inside a warehouse in Santa Clara, Calif., where all of the shelves and counters and other store elements were put on coasters. Every morning, Steve Jobs would walk into the warehouse and move things around. Maybe again in the afternoon. This continued until everything was in its proper spot.