Carcassonne is definitely one of my all time favorites.
It is equally great game when played with friends or when played solo.
One of the solo Carcassonne versions was suggested by Christopher Plummer.
The goal is to build a city within a city, by scoring large amounts of points.
This version is the least complicated Carcassonne solo variant, good to be played when you feeling a bit tired and you need something to clear your head, or when you simply feel to lazy to place and remove followers :)
Here is a photo from one of my victorious games, using base game and Ins and Cathedrals.