In the 10 minute challenge thread there was a small side discussion about GeoControl, a terrain editor and generator.  I've had a little spare time to start to learn its controls and capabilites and I find it an amazing and perfect compliment to Bryce.  Its not cheap when compared to the $2 Hexagon,  free Bryce 5 , and free Wing3d but it isn't a bank buster also. ($87 USD). 

I thought I'd show you a small example to the terrains it can generate and I have only scratched the surface.  All the terrains here are single 4096X4096 terrains that take about 2-3minutes to generate and export to Bryce. Once in Bryce you can continue to modify it in Bryce's terrain editor.  Each terrain I applied a simple (usually preset mat from B6) and rendered in a context I felt it fit.

This one I free handed the water into the gorge.