World view to RTS view detail level zoom

I'm looking for a way to handle not just large terrain (continent-size, 2000km by 4000km) but also provide a smooth zoom between a full map view and a detailed view. I don't need FPS level, but RTS level - individual buildings visible, map size maybe 2x2 km or there about.

I've found many assets and approaches that can handle the terrain size, with streaming and stitching, etc. - but I haven't yet found something that can give me the "zoom from world view to close-up view" ability that is a major point I want.

This also brings its own challenges - for example, I can't use fog to hide the lack of distance. But that's another issue.


Any pointers, assets, anything?


I should mention that at this point I'm open for both traditional Unity terrain, mesh terrain or voxel terrain.