Creation Kit - Kit Pieces

During the summer holidays I had a go with Skyrim's Creation Kit. The tutorial's showed me how to make a dungeon and I found out that the majority of the buildings in Skyrim were made using kit pieces.
Kit pieces are large and varied pieces of environment that fit together to make the dungeons and temples you explore. You can build large environments quickly and easily by simply dragging and dropping the desired piece into place.
This method seems to be best suited for large open world games like Skyrim as it would minimise the time and effort as well as add the variety to sustain player interest.