Bona World Editor
Bona world editor is a Unity editor extension to easier create scenery by simplifying the process of adding objects to your scene. The extension adds a new Tools Window and a new asset type called an Asset Set that you can customize to suite your need.
The editor is easier to use for outdoor environments that is displayed from a top-down perspective. To use it, you first need to create asset categories. These are collections of GameObjects you want to place in the world along some scaling and rotational data for them. These are combined into an Asset Set which can them be used by the Tools window to allow you easy access to all these objects instead oh having to drag-and-drop down from arbitrary places in the Assets hierarchi. The look and feel of the editor is heavily inspired from Blizzard's World Editor for Warcraft III.
Disclaimer! This package contains mainly the editor extension. Any assets including models, textures etc are only as examples of what the editor is possible of and are not guaranteed to be of any considerate quality.