The demonstration that Batman: Arkham Knight got during Sony’s E3 press conference on Monday evening was definitely one of the highlights of that showing (even though it showed Batman using guns, and Batman does not use guns). The game looked excellent, and Gotham looked like a veritable (dark and gloomy) sandbox for Batman to traipse through.
Gotham City in Arkham Knight is more than five times the map size of Gotham in Arkham City, making this the biggest map in the series yet; this was made possible by the additional power of the Xbox One and PlayStation 4, and was what necessitated a shift to next gen only consoles. That same extra power also let Rocksteady make the map as vertically extensive as they wanted.
Which makes sense, as the city, which will be traversed in the Batmobile, must feel like a place you want to dick around in in the first place.