"Sidewalk Vault Glass...A deep childhood memory"

     Growing up in the 1950's, I remember being completely fascinated by the colored glass embedded in the sidewalks of my hometown.  I recall my dad telling me the glass squares let the sunlight into the basements of the stores they were adjacent to, and later on I learned that these little glass squares are actually prisms that were originally designed for sailing ships in the early 1800's to allow sunlight into the holds below deck. By the late 1800's the technology had extended to city sidewalks outside stores to allow natural light into the basements.
   
     My favorite vault glass in Portland is located across the street from the food carts along the north sidewalk of the Galleria Building on SW Alder Street between 9th and 10th avenues.

http://glassian.org/Prism/Vault/index.html