This is the 11122nd most frequent Turkish word.
duvarın
"Of the wall" (possessive form).
In this case, "duvarın" indicates the position, specifying the location as the 'area beneath the wall.'
Şimdi duvarın altında olan kutuya bak.
Now look at the box beneath the wall.
Here "duvarın" specifies ownership, referring to the wall's inherent feature, its color.
Duvarın rengini değiştirmek ister misin?
Would you like to change the color of the wall?
Here, "duvarın" implies possession, indicating that the painting is situated on "the wall's" surface.