Don't know if it's still available, and it may be of limited use, but at daz (ugh!) Fober's "the lake" has a companion, don't remember what it's called, but it's a winding road through a hilly landscape.  Has all the props to make what you can with it.  Not a freebie though, and like I said, maybe no longer available.  Might also look for "Worldbase Extreme", but no trees or anything else included with that.  Both released about the same time, just don't ask me how far back.  Both at daz.

Doric.

Worldbase Xtreme is still available at Daz3d but is expensive, at least I thinks so.  It dates back to around 2006 and even the promo description talks of Poser 5 and 6.  Terradome and the more recent Terradome 2 both up the game and the latest version is almost the same price. 

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.