IMO half the giveaway of backlots is just the scale. The urban settings feel about 70% size. The streets are too narrow. The buildings have a bit of forced-perspective shortness in the upper stories. Even the sidwalk curbs aren't quite as tall (I have walked around some backlot sets).
There is also the short lateral distances. To keep the backlot sizes manageable, the streets never continue in a straight line for more than a couple of (short) blocks. There is always a sharp turn or a T-intersection or something to cap off the view.
Of course the height trickery is done to make the fake buildings look taller. But some of the cheating is to make the actors look taller, too. It's routine for set builders to make the height indicators (doorways, visible interior ceilings, etc) a couple inches lower than normal.
There is also the short lateral distances. To keep the backlot sizes manageable, the streets never continue in a straight line for more than a couple of (short) blocks. There is always a sharp turn or a T-intersection or something to cap off the view.
Of course the height trickery is done to make the fake buildings look taller. But some of the cheating is to make the actors look taller, too. It's routine for set builders to make the height indicators (doorways, visible interior ceilings, etc) a couple inches lower than normal.