Here's a map of what was once known as River Country -
http://www.wdisneyw.co.uk/rcmap.html .
In all honesty, there wasn't really much there - Two (maybe three) body slides (which when I last visited felt unsafe to me - I felt like I would go over the sides), a slide that was literally 20 feet long that dropped you 6-7 feet into a pool, and a tube ride which I loved. It was kind of like a lazy river that constantly went downhill. There were whirlpools you could get stuck in and such - I remember loving it as a kid.
Still, there wasn't much to the park, but there was a certain charm that is definitely missing from Typhoon Lagoon and Blizzard Beach (both of which seem "plastic" to me). Nevertheless, the fact that those parks use clean, chlorinated water and River Country used water from Bay Lake more than makes up for the lack of "realness" that River Country had.
Do I miss it? Yeah, a little (especially that tube ride), but it won't ever open again, so there's no point in dwelling on the past.
Here's a couple more pics that give you an idea of the slides -
http://www.wdisneyw.co.uk/photorc.html - However, I don't think the pic on the top right is River Country.