A familiar street becomes newly interesting when you follow one repeated feature. Doorways provide a manageable subject because they connect the building with everyday movement. Their frames, thresholds and surrounding surfaces offer plenty to observe without requiring access to private interiors.
Choose a short section of public pavement and record a few examples. Describe shape, colour and the relationship between the doorway and the windows above it. Avoid photographing residents or private details, and respect restrictions around buildings.
Look for variation within repetition. Similar openings may use different materials or show different kinds of wear. Those observations can suggest questions, but they do not by themselves establish the age of a building or the history of an alteration.
At home, arrange the notes in walking order. This preserves the experience of moving along the street rather than turning the examples into an artificial ranking. One focused walk can become the first chapter of a much larger personal record of a place.