What makes a world 'vast'
This is more of a general RPG topic than SE, but more specific than Gen Gaming, so... whatever.
What makes a video games world 'vast' to you. In the thread about what you liked about each FF I noticed a few people praising FF12 for having a vast world. One of my main complaints about FF12 is the world feels very diminutive. So obviously we aren't all judging by the same criteria here :p
So, what makes the world feel 'vast' to you? Or conversely, what are the flags that make it feel small?