The long view
The longest sightline in a home — how far the eye can travel from a doorway before something stops it. A room feels as deep as the farthest thing you can see from it, so protecting the long view borrows distance the floor doesn't contain.
The eye borrows distance
A gaze that runs from the front door through to a balcony makes the whole flat read as one generous space. Lowering a partition or glazing a wall to free the long view is among the highest-impact Extend moves.