Landscape with meshes built in?

I am learning a lot as I use Unreal but I ran into something today that I just cannot find any information on. I must be googling the wrong phrases.

I was testing out a camera system in a demo map from the Urban City pack from polypixel and noticed that the roads and sidewalks are somehow built into the landscape? There are no mesh assets for either and they all just select as the landscape. I’ve never seen this before and trying to dig around in the level I could not figure out how that is done. Is there any kind of documentation about setting this up?

Probably sculpted on the landscape with either brushes or splines.
to check if that’s true look at the landscape material. It would have to have the brush to paint on a road.

if they are made with splines, then you have to go into landscape/splines to be able to select the road-splines. then in details look for the meshes used in the spline.

Thanks MostHost LA and Vollgaser for pointing me in a direction, I’ll look into that more and see if it is the case.