What are those grids of glass in the sidewalk and why are they purple? (kqed.org)

Article summary

Vault lights, also known as sidewalk skylights, are glass grids embedded in sidewalks to provide natural light to subterranean spaces. They were originally used on ships and later adopted for use in cities, including San Francisco and New York City. The glass in these vault lights often turns purple over time due to the effects of UV rays on the manganese dioxide used to clarify the glass. This technology has been used in various iconic projects, including the illumination of sub-sidewalk basements and abandoned storefronts.

Main themes

• vault lights
• urban infrastructure
• historical architecture
• natural lighting
• city development

What commenters say

• The use of vault lights is a fascinating example of historical engineering and architectural innovation. Some cities have underground tours that showcase these vault lights and other hidden infrastructure. The technology behind vault lights has potential applications in modern greenhouses and vertical farming. The legal and maintenance aspects of vault lights, particularly in relation to property ownership and public rights of way, are complex and vary by location. The discovery of vault lights can be a surprising and interesting experience, even for longtime residents of cities where they are found. The use of vault lights in different parts of the world, including the UK and Scotland, highlights their widespread adoption and historical significance. The maintenance and repair of sidewalks and vault lights can be a significant responsibility for property owners, who may be liable for costs and upkeep.