Brussels, you said?
Well, by saying that you are in / live in / head to Brussels, you are probably referring to Brussels city or to Bruxelles-Capitale Region. Both are correct since the Region is so small that you are not even aware of that it comprehends 19 communes... and that the latter are worth a visit as well.
Besides, current configuration of the Region was defined in June 1989. On June 18, 1989, Brussels people elected their MPs so as to grant the region with same status as Wallonia and Flemish Regions.
19 communes are, in French and Flemish:
Anderlecht | Auderghem - Oudergem | Berchem-Ste-Agathe - St.-Agatha-Berchem | Bruxelles - Brussel | Etterbeek | Evere | Forest | Ganshoren | Ixelles - Elsene | Jette | Koekelberg | Molenbeek-Saint-Jean - Molenbeek-Sint-Jan | Saint-Gilles - Sint-Gillis | Saint-Josse-ten-Noode - Sint-Joost-ten-Node | Schaerbeek | Uccle - Ukkel | Watermael-Boitsfort - Watermaal-Bosvoorde | Woluwé-Saint-Lambert - Sint-Lambrechts-Woluwe | Woluwé-Saint-Pierre - Sint-Pieters-Woluwe.
For instance, I use to say that I live in Brussels. That's true since my homeplace is Woluwé-Saint-Pierre, a municipality in Region of Bruxelles-Capitale... but it's not in Brussels municipality.
Official Languages: French and Dutch. You mainly hear French in the streets since 70-80% of Brussels population is "francophone" (French-speaking). Apart from that, you may hear at least Arab, African languages and languages of countries that are EU members... and of course, Dutch. In winter: smell of waffles in Brussels center streets; hot chocolate in heated cafés; music in Rue des Tongres for / while Christmas shopping
In spring: cherry blossom and season opening as for terrasse sitting :-)
Season opening as for walks through forests and green areas.
It's the season I enjoy most to go to markets. Don't ask me why. I hate doing it in summer when it's crowded and sticky hot.
In my study years, hearing tennis rallies, from a tennis court near my house, while I studied for my June exams. Frustrating!
In summer: heat and very often rain accompanying sales month (july)... and evening at Zizi and Aux délices de Capoue (ice-cream with Belgian speculoos). For that, see my Must-see activities tips.
In autumn: frenzy atmosphere when people return from holidays. Shops are packed with scholars and their mums trying to buy scholar stuffs. One has to buy new autumn cloth as well. A bit of rain. Hot chocolate season starts.