Mesh terrain workflow for 8k worlds (it freezes and crashes)

I’m making a 16 x 16 km map with 2 m vertex spacing (working in a Landscape system). Can’t make it work with Mesh Terrain. I can create the mesh partition rectangle if I check Save and Unload, but trying to load it all in the World Partition Editor quickly eats up the 64 GB of RAM I have. Loading just a bit seems to work until I load too much, and then Unreal just becomes unresponsive and I can’t even move the window. This doesn’t seem to be about running out of memory.

I tried to Import Heightmap. Works until I try to load a region, then I get a Registering actors message and Unreal goes unresponsive.

I thought of exporting the landscape as an OBJ and importing as a mesh, to use in Mesh Partition. The resulting mesh file was 16 GB, and I couldn’t import it as a mesh.

I am trying this in Empty Open World levels after realizing I can’t make a level using the Content Drawer (that caused worse problems). I didn’t change the World Partition setup - should I have?

Is my approach wrong? What should I do? Should I use Landscape generally, and add small areas of Mesh Terrain where I need overhangs? Or is the old workflow still better everywhere for such a large map (though I’m surprised how large 8k seems to be as we’re routinely handling 4k textures now)?

Should I make a low-resolution rectangle and tesselate it using a modifier? Would that be better even for the same outcome resolution?

One thing is that I would really like to see the whole level, at least somehow, in the editor while working with it (as with a Landscape), and occasionally most of the level would be visible in the game as well. In my understanding, the finalized nanite representation would have efficient LODs, but the intermediate editor representation doesn’t.

As far as I can tell, such large maps can’t be handled the same way that small maps are in tutorials and documentation, and I was unable to find any insights on this.

Seems I can make a 2k x 2x map IF I do it in a fresh project. In another map that already contains other levels where I tried making various mesh terrains, no luck. 4k x 4k in a fresh project also freezes Unreal, even as if there’s no evident excessive memory use (Unreal 5.8.0 shows up in Task Manager as using ~17 GB). There’s no disk or network activity, but 16 - 25 % CPU. Could be that Unreal is doing something in a single thread, but it’s certainly hugely slower than making a smaller map, much more than the difference in size would suggest.