There are a couple of reasons. Firstly, I tend to be partial to forests and mountains - they are somewhat similar to what I have grown up in (though some of my cliffs and mountains are not quite as tall as I remember as a child
![Razz](images/cartographer/smilies/razz.gif)
) so that tends to narrow regions I would focus on.
Waterfalls are another fascination for me; I have gone biking and hiking to look at waterfalls before (much to the amusement of my family and friends - not certain my sister will ever forgive me for the 'trail' we biked down one time to get to a waterfall) and, so, why would I not in a fantasy world?
The caves are a bit harder to explain. I would feel very claustrophobic in them but the idea of the caves of moria / helms deep kind of overpowers that. Who has heard of a fantasy cave that does not look absolutely splendid (at least when the lights are on)?
The fact they are near each other just makes me journey easier (and I can avoid the trip across the borderlands).