Sidewalks That Act Like Skylights

Before electricity became cheap, cities used glass prisms embedded in sidewalks to illuminate dark basements. These clever glass blocks redirected sunlight deep under buildings, turning underground spaces into bright, usable rooms.

During the 19th century, urban architects faced the challenge of lighting deep subterranean areas without electricity. They installed thick, durable glass prisms directly into the pavement to serve as walk-on skylights. By using specific angles, these prisms could cast natural light horizontally, reaching far beneath the street. While modern light bulbs made them less common, you can still find these beautiful vintage glass tiles embedded in older city sidewalks today.