There is a quality to the urban sidewalk at night after a rainy day nowhere to be found otherwise, except maybe on a very quiet night with bright moonlight on a lake border.

This quality is the reflection of city life in puddle pools.

The eyes of the casual observer looking up in a city at night while walking or biking would see buildings, trees, city lights and only somewhere in between patches of dark sky where the stars become invisible, by contrast. When looking down, most urban surfaces have a texture and color that will make them appear dull in dry weather, but somewhat bright and sparkling with reflections of city lights when wet. The more remaining surface water, the more reflections of city lights are to be seen; areas with running water become particularly noticeable through the luminosity of the combined reflection of many light sources.

That is, except around areas where the surface water is sufficient to create a still pool, i.e. an area with no apparent texture. There, unless the angle is right and the inverse path of reflected light from the observer’s eye crosses a city light source — an unlikely occurrence in moderately dense European cities, given the relative rarity of city lights — there is perceptively nothing to be seen in the pool’s reflection.

Only the Universe, through the small frontier of stars created by the pool’s borders. At day, these patches of water would appear white or blue from the sky colors… At night, they make reality vanish, and make the city darker.

Next time you go walking or biking at night after a rainfall, please take a few seconds to look at the ground. Look at the bright areas, and notice how the pool in the middle of the bright area is more black than any other surface in the city landscape. Then consider, as you would with reflective surfaces otherwise, what the world “on the other side” looks like.