There are big open-world games out there, some bigger than GTA5 - but there will be none stuffed with as much content, Rockstar believes.
"In terms of raw man-hours, this has been way in excess of any project we've done at Rockstar before," Rockstar North art director Aaron Garbut told Buzzfeed.
"From the outset, we wanted to ensure that not only was the world big but that it was absolutely packed with character and life. It's levels of magnitude above Grand Theft Auto 4 in terms of what we've done on the environment side.
"I know there are bigger games out there geographically, but I don't think there are in terms of content. I want to stress that not only is this world huge but it's absolutely handcrafted. Every little bit of this world has had a large number of extremely talented artists pore over it. There's always something to discover, something weird or interesting to see or interact with.
"It's absolutely not a massive, empty world."
Every tree is placed with consideration; buildings aren't copied and pasted; terrain isn't procedurally generated "to pad it out". "I don't think many people will ever see everything we've put into the world," he said.
"We used to call Liberty City a living, breathing world, but this is way beyond anything we've done before."
GTA5 has strong ties to GTA4 owing to both games being produced for current-gen consoles. GTA4 arrived two-and-a-half years into the console generation, GTA5 at the end of it - and it's remarkable how much better it looks.
"Grand Theft Auto 4 was our first headlong jump into current-gen consoles," explained Garbut. "We had a lot to learn in every aspect, not just technically but artistically and even in terms of production. We moved from effectively building a world out of some roads and boxes to a much, much more detailed creation. That first jump was really hard.
"Since then, though, we've had a lot more experience. We're comfortable building assets at this level of detail and our coders are comfortable with the machines. We've pushed them much, much further than before."
Sense of scale was the most important thing Rockstar wanted to achieve, and believes it has with a non-limited draw distances and lights drawn so far back. Heat haze and cloud shadows and advanced fog emphasise this even further.
Streaming technology helps add all the extra detail, ensuring the world is not only bigger than GTA4's, but also "much more detailed". "There's just so much going on," he added, "not just on the backdrop of the world but in the life on the street."
You'll be able to see it all for yourself first-hand on 17th September.
Below are couple of spoof political videos created in and for GTA5.