How big of a map can Unity support?

I have been working on this idea for about 3 years now. I finally did the math to scale out my world.
625 miles by 500 miles or 312,500 square miles. Now (because I’m a big dreamer) I am planning to make it actual size.

So on to the question.
Can Unity support a 312,500 sq mile map or will i have to break it down in to many smaller maps that load and unload?

Well, I guess it depends in the complexity of your scene (number of objects and triangles), but you might probably need to break it down. I think you will have to test to find out.

There’s also another problem. Unity works with floats, with such big scenes, you might find spatial jittering problems when you move far from the center. I recommend you to check it out, just move your camera to distant places and play around.