Best way to store textures for massive maps?

So say you have a game world as big as skyrim. How would they store/load all their textures efficiently? The only method I can think of is splitting up the terrain however I would imagine this causes problems with physics and might lead to glitching through the floor. Additionally this would require hundreds of texture maps for each section.

Is there any other way?

Firstly - atlases. For all the props you can use one or two textures for each map(e.g. 1 diffuse texture, 1 specular and 1 normalmap for all opaque props and the same setup for all the transparent ones. You can place each object’s texture(when creating atlas) in gird form. It is that you have, as example, eight 256 textures and one 512 texture - than you create 1024 atlas and place textures in grid where each 256 texture uses one tile while 512 texture uses 4 tiles. And for object UVs you go in the Blender’s UV editor, select all the UVs of object and scale it down(for example, the 256 is 4 times smaller than 1024 atlas size so you select all UVs and do S + .25). Than you move those UVs, but do it this way - select all UVs of object, press G, than axis letter(either X(horizontal) or Y(vertical)) and type in numbers. For example, to move it half tile up you do G + X + 1 + 2 + 8. And than you move it by tiles(Instead of 128 use only 256 for moving it). As result you can make all the props in your scene use just one texture and one material. And using specular map allows the material to look good on each prop. For terrain you have few base textures(e.g. grass, gravel, dirt, cobble path, rocks etc.) and a stencil texture for each terrain(it can be 512, for example, because the textures will just blend and they usually doesn’t require very advanced blending, but you may decide stencil to be up to 2048). And you use nodes, go on the stencil, plug it’s color in seperate RGB. One stencil can provide up to 5 textures. I will add a .blend to show you how after I make it.

They’re just few hints, but they can come really handy later:)