The red-brick deYoung Building was covered with 1950s spandrel-type panels for most of my time working downtown, an effort to make the building look modern... which appears to have done a lovely job preserving the more attractive building beneath.
The upward expansion wisely has a different color, texture, and more modern bent, and remains impressive to me. (I don't know what was done to have the original building support the additional weight, but it looks fantastic.)
