Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Terrain Former Free.
Terrain Former v1.7.11
Terrain Former is an intuitive and simple terrain editor for Unity with support for multiple terrains, allowing for terrains suitable for even the biggest open world games.
– Full multi-terrain support—sculpt seamlessly across mutliple terrains.
– Flatten (with Bridge, Extend modes),
– Set Height,
– Paint Texture,
– Heightmap Importer, Heightmap Export to EXR,
– Mould (formerly Shrink Wrap),
– Generate—generate terrain that follows a curve (w/ linear and circular modes)
– Terrain Grid Creator Wizard,
– All tools work across terrain grids
Terrain Former addresses all of the major issues with Unity’s built-in terrain editor, such as the painfully slow smoothing tool and its constrained brush size.
Note: Details (rocks, grass, etc) and trees tools are planned but will be coming in a future release of Terrain Former. You can however in the meantime, easily switch between Unity’s terrain tools and Terrain Former.