I’ve had experience in creating levels in both Unreal Engine 3’s level editor and Source Engine’s Hammer editor yet Unity’s way of constructing levels is very different in that it does not use a sort of “snap-grid” way of constructing basic geometry just like the previous two engines mentioned. So far based on what I know Unity’s way of making levels is through basic shapes such as cubes or cylinders that need to be extruded and strangely placed evenly, terrain, and use of custom models. The terrain construction and model creation is universal with most modern game engines yet level construction is what I don’t get in Unity. How do you properly construct levels in Unity and where can I find tutorials on actual level construction rather than level design?
Search for Vertex snap. As far as ‘model creation’ that’s not the real focus of Unity or UDK for that matter, you create models in 3D model apps and then import them.
There are many, many questions/answers, tuts, vids and other resources on level creation, please search.