National holidays in Belgium are:
December 6th is a traditional day in Belgium, people celebrate what is called “La saint nicolas”, children wake up to find all sorts of gifts and candies in the house. Parent tell them that Saint Nicolas brought gift during the night to congratulate good children.
During february and march a lot of “carnaval” are organised, it’s parade where people dress up and walk around town.
One of the most famous one is in Binche. http://www.carnavaldebinche.be/
In summer, Kermesses are organized in many cities, festive events with lots of activities for children, carousels, duck fishing, bumper cars, etc.
Flea markets: take place everywhere throughout the year, allows you to buy items at a lower price (http://www.brocantes.be/fr/agenda/province/Toute_la_Belgique/Tous_les_evenements)
For more information on culture visit:
French-speaking community: http://www.culture.be/
Flemish community: https://cjsm.be/cultuur/