It wouldn't be the real Vegas if massive parties and general nightlife debauchery weren't a part of This is Vegas. The rise of the super-club has been meteoric with some casinos even going so far as to pay celebrities to show up at major events. This is Vegas takes this party mentality to heart, integrating the nightlife into the game itself. Of course, it also has the over-the-top twist that the game is shooting for.
This is Vegas is an open-world game and so the outdoor areas are quite expansive -- roughly on par with GTA III IGN were told. The catch is that all of the fun stuff happens indoors in Las Vegas. This is Vegas takes this to heart with massive indoor environments to explore. The casino gambling floors are there as well as clubs and a whole lot more.