This is a Custom Terrain that I have made for Reer123, His request was 'a windy river leading through a valley which is bordered by mountains. At least one hundred blocks of space between the river and the mountain border. I would like there to be a forest made up of Spruce trees and custom trees (like willows with long hanging leaves).
Make the terrain bumpy and not flat or "Minecraft Vanilla" like. Add caves into the mountains, small ones with fences outside them (like blocking the way in). Have a road (Messy Medieval Style) running by the river and crossing near the centre of the map. The river should be around five hundred blocks in length.'

I hope I have made it right for you :)
-Zamarak825