This is a paid asset, but now you can download Ferr2D Terrain Tool Free.
Detail this asset from Unity Store: Original Link
Ferr2D Terrain Tool v2.0.3 (Latest version)
Ferr2D Terrain Tool v2.0.2
Ferr2D Terrain Tool lets you quickly create hand-crafted 2D/2.5D landscapes and levels!
Version 2.0 just released! Tons of great new features!
No placing tons of ground sprites, no manually tweaking piles of collider objects, and definitely not bound to a grid! Just pick a terrain material, and draw a path. Edges switch texture automatically, and colliders create themselves!
[ Site | Video | Demos | Forum ]
-Path based design for rapid development and iteration!
-An easy-to-use path editor that allows for extreme control!
-4 auto edges, plus additional edges through edge overrides!
-Flexible settings: make interiors, exteriors, plants, pipes!
-Smart snapping, world snapping, relative snapping. Snip snap!
-Wavy shaders for grass, leaves, and other effects!
-Fast per-pixel and per-vertex 2D lighting shaders!
-Optimized with mobile performance in mind!
-2D or 3D colliders, so you can collide however you like!
-Collider corner settings for every occasion!
-Separate physics materials for different edges!
-Custom editors for quick creation of terrain materials!