A copy of the near window slides onto the far one: the same size.
Bigger or smaller?
Which window is larger?
Which window is larger, the one on the near wall or the one on the far wall?
Neither: the two windows are exactly the same size, though the far one looks bigger.
Why? The lines of the passage tell your brain that the far wall is far away. Something far away that still looks this big must really be big, so your brain makes the far window look larger, as in the Ponzo illusion.
Picture: Drawn by Science Playground · Wikipedia(opens in a new tab)