Level Design?

I am planning on starting to make a game that is in the MMORPG type, but i want the world to be huge. So how huge of a world can i have?

Any help will do.Also need Level Design Ideas. along with other things such as monsters.

Thanks for your time. ~Bob

In Ue4 it could be very big.
Try it, disable kill z and let your char fall.
You can fall very long.
When you make big things, you have to fill them.
i would start small and connect - repeat - someday it’s big.
Things have not to be complicated to be big.
Here an example from me, i made yesterday in perhaps 4 hours, from idea / pencil paper / blender / ue4/ blueprinting.
UE4 makes me happy.

While the possible size of the world is ridiculously large, I would say start by creating a moderately sized introduction area for proof of concept. Think beginning of Skyrim or World of Warcraft sized depending on what kind of MMO you want. Also if you are creating a large world (Depending on type of game) you can usually get away with fewer details, while a small linear game needs constant diversity, rolling hills and plains populated with some enemies and the occasional structure/ loot/ side quest can be just as interesting.

it would be best if you start with a idea for a game, its environment, world and creatures that live in it.