Map Scale Guide?

Hey guys, Just looking for abit of help with my scaling.

http://puu.sh/e8MRV/b4bb2c55f9.jpg (Something I made for example not actually it).

What scale do you guys generally user for everything. I'm thinking the size of that first slope should be the size of the slope that goes into the water.

What do you guys use as a guide for your scales though.

(On a side note, is that old island prefab that used to come with the older unity's still around