I'm trying to remember a picture book I read when I was young but no amount of keyword searches will bring it up.
It's set in a grown up's world but everywhere in the cracks in the walls, hiding in nooks and in random places are little windows, doors, houses, hot air balloons. A whole undiscovered world, which unless you're looking for is invisible.
Beautiful illustrations. Some of the doors look like this:
Thank you
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