You could probably use any Wordpress theme that had a design and feel you like. I would use a good events plugin such as Calendarize It. That plugin makes it easy to set up a nice calendar of events. You can make specific calendars for each country, category and city. They could view them all on one calendar or filter down to specific locations. You could even enter the venue information for the events as well. It's a pretty decent plugin. You can see an example of it working here: http://tvqma.org/schedule