Check out this GTA IV video running the game on PC at 3840x2160.
The video courtesy of YouTuber Unreal is giving you a look at what GTA IV looks like when running at 4K resolution settings.
The effect has been achieved using iCEnhancer 3.0 software to render out the game. Unreal used an i5 2500K (overclocked at 5Ghz) with a single GTX670 graphics card (overclocked 1300/7200).
The results are pretty smooth as you can see from the video below which is best viewed at native 4K settings.