Vish02
As mentioned the GE90 engines are certainly very large as a visual indicator, but other B777-300's may have the slightly smaller GE series and yet are still large compared to the RR Trent 800.
Have a look at the front of the main undercarriages, you will see a very large diameter actuator connecting the truck to the oleo. the earlier -300 models have a smaller tilt actuator that is almost not noticeable from a distance.
TW