Increase expansion radius 
The feature "Increase expansion radius for fortresses/cities" enables you to attach castles and fortresses to your fortress/city center from greater distances.

As soon as you created a fortress center (city center), you see all possible habitats in the predefined attachment radius. Now you have the possibility to increase this radius by a certain value (Fortress: +3/City: +6), so that you can attach habitats from greater distances. The usage of the feature requires Gold Coins (Fortress: 500/City: 1000).   

The increase of the attachment radius is just temporary (12h), so you have just a few hours to start the attachment process of a chosen habitat that would usually lie out of range. Once the attachment process is started, it will not be canceled after the runtime of the increased attachment radius has ended.