Sketchup is addictive! I've spent a lot of time creating a three dimensional model of the house I grew up in. You don't know how many details you have forgotten till you try to do this.
I went on to do Sherlock Holmes flat. I started with the PBS version and then modified it with a few features from the Connan Doyle stories left out of the TV set. However, Doyle seems to have not had a consistent notion of the layout. So I have had to make compromises.