http://www.pegasushobbies.com/gm_main.htm#
Scroll down near the bottom here and check out the "Toxic River."
I have that and, while it's not the BEST in the world, it is VERY GOOD. Add a little paint retouching, and it can be GREAT.
It's 4' in length and (I haven't even LOOKED at mine in a while) I THINK it comes with a couple curves, too.
Overall, from bank to bank, its' footprint is around 4" wide.
At $30 US, it's not a bad purchase, either.
I have quite a few pieces of theirs:
5001 Idol of the Skull
5011 Alter of Evil
5030 Orc Idol
5032 Dark Spirit Stone of Rage
5090 The Muddy & Bloody Trenches
5130 Toxic River Set
The rest of my group owns some of those, as well as:
5006 Bunker I
5007 Bunker II
5045 Tower Building
5050 Chapel Building
5062 Ruins I w/Interior
5132 Toxic Bridge
Every piece is quality made gaming terrain. It is solid and decently painted.
I can't recommend Pegasus enough.
Eric