Sidewalk Prisms

I stepped onto the row of thick glass vault prisms set into the cast-iron sidewalk frame. Just beyond the cellar doors, the grid of circular lenses ran parallel to the building's granite foundation. I dropped to one knee to examine the nearest glass roundel. Its surface was clouded with fine street dust, but brushing my thumb across the center cleared a circular viewport straight into the vault beneath the sidewalk. Looking down, I could trace the vertical outline of a concrete support column anchored directly under the street. The heavy iron lattice did not flex a millimeter under my boots.