This season's Spacing Magazine has an article on Vault lights. Seen as glass tiles imbedded in sidewalks, these were once used to pull natural light into basements otherwise without.
The article speaks to the rise and fall of popularity and as with most clever design materials the practicality of maintenance and upkeep leading to the fall. Having just completed a project which included legalizing a basement apartment, I found myself researching all manors of pulling and achieving the city regulated natural light requirements (not a simple feat). I considered using Tunnel lights which basically function the same as these vault or prism lights. Sunlight passes through the surface and then through a prism which angles the light inward, illuminating the space with natural light.
According to Spacing the only known example of vault lights remaining in Toronto "is the glass in front of the shops at 2869 Dundas Street West (near Keele)". These were perhaps not as practical as today's modernized tunnel skylights but without question, so much more charming. This is one of those times that I feel remorseful, for our having lost something, I didn't know existed before today.
source[spacing magazine, issue 16]