Great outdoor WADs?

I've been looking for ways to make more interesting nature areas. I know the DOOM engine isn't exactly ideal for recreating The Great Outdoors, but perhaps yous might know of any WADs that have done an exceptional job of creating jungles, forests, or nature in general. Suggestions?

I think Final Doom: The Plutonia Experiment contains quite a lot of outseide areas.

If you prefer jungle style, try Scythe 2 maps from MAP20 to MAP25, or dannebuniga's recent WAD "Combat Shock 2" also contains jungle-style levels.

Two wads simply named The Island (island.wad) and The Island 2(island2.wad) have large outdoors jungle like areas.

These threads might give you a few ideas:
http://www.doomworld.com/vb/showthread.php?threadid=56738
http://www.doomworld.com/vb/showthread.php?threadid=55467
http://www.doomworld.com/vb/showthread.php?threadid=49677
http://www.doomworld.com/vb/showthread.php?threadid=32641
http://www.doomworld.com/vb/showthread.php?threadid=25848

not ever mentioned in these threads before: Grotesque CTF by Alfred (grotectfr.wad)

zdoom maps (doom in hexen format), rather flat, but the visuals are great. and the last map looks simply stunning.

I personally love the forest that was created for Grove. It may not be exactly what you were looking for but it always comes to mind. If you think your computer can handle it you can check out the original version here, which uses a ton more sprites and is likely to cause a massive frame rate drop.