How to make a character's vision more realistic?

I have a game with a really big map. If I raise the “Far” value of the main camera, it won’t look realistic because nobody can see that far, plus the game would run very slowly. If I made it small, then the world would just seem to “appear” when the player moves. If you’ve ever played a game like GTA V or Skyrim, they have huge maps. The player can’t see the entire map, yet when they move, the map seems to load smoothly like it would in real life. So, how would I make it so then the maps that my game takes place in loads realistically?

You can use level of detail (LoD) which comes with pro.

Or make your own LoD. Make 2 models of everything. When stuff is really really far you dont render some objects, far you render the low detail model, closer you turn on the high detail renderer.

Also the player can have 2 cameras, one for far that culls certain layers, one for close range.