The "cast iron district" that is SoHo in Manhattan still has some sidewalks and stoops that look like this one, on Wooster Street between Grand and Broome Streets:
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Note the raised nubs at the interstices between the glass, which provide traction in rain.
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The stairs are cast iron, and you may be wondering why the original 19th century manufacturer would go to the expense of perforating them with glass circles. Those circles are actually lenses, and they serve a clerestory purpose. As with many other manufacturing districts around the country, SoHo's heyday antedated electricity and artificial light. Many of these types of structures were fronted by hollow sidewalks, with basement workshops and storage spaces directly beneath. Topping them with these "vault lights" admitted crucial illumination into the space.
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Interesting historical tidbit: Vault lights were invented in 1845 by New Jersey native Thaddeus Hyatt, who became fabulously wealthy from them. An abolitionist, Hyatt used his fortune to fund anti-slavery organizations and was thrown in jail for his troubles. He eventually retired in England, where he died in 1901 at the age of 85.