How big can my game world be?

Development World Creation
1

i want to make a huge rpg world sort of like a continent.
my only question is how big can my world be?? before i start having fr lag?
im pretty sure the only way to do this is to code parts of the world to be (off). until needed.

2

here is some info about landscape sizes

3

also check out the the Kite Demo, which is an open world.