To configure the Places plugin:
You can configure the color that highlights the place name when something happens in your place. You can use multiple color codes. For example: %xh%xc
These are the markers used in place names.
The game will periodically clear out empty places from rooms. There is a cron job to control when this happens. By default it does this every hour. See the Cron Job Tutorial for help if you want to change this.