As a photographer, when I walk in the streets, my eyes wonder towards all directions. Not only am I interested in objects outside, on the streets. Every so often I also pick up a glance of interesting interiors, visible from the street. Through the glass of a window or door.
When the composition, lighting or color is interesting enough - and nobody is watching - I take out my camera, place the lens hood against the glass, make the composition and ... shoot !!