Situated in the city center of Brussels, from June on, the Beursschouwburg temporarily moves its Beurscafé to the rooftop on the fifth floor. This rooftop bar is a really nice alternative venue, with good music, happy people and a nice panoramic view over Bourse, the ancient stock exchange building.
The Beurscafé is housed within the Beursschouwburg, a cultural center for art and music. The rooftop terrace opens in the warmer Summer months as a nice place to spend the night out. They regularly host events, such as exhibitions, live music or open-air movie screenings. Check out the calendar for more information about the events, many of which are free.
At lunchtime, you can take your own food up to the roof to have a picnic in the Brussels sun. Of course, you can also just meet up with friends to have a drink here. You can choose from (a small selection of) beer, biological wine, several cocktails, and soft drinks of course. With prices varying between 2 and 8,50 euros, the drinks are modestly priced for being in the center of the city.
The best time to go would be in the evening on a week day. Chances are it is not too crowded then, and I think the terrace is especially lovely when they turn on the party lights.
Standing on this terrace, you can overlook the rooftops of the surrounding houses, the Dansaert street on your left, and Bourse on your right.
Keep in mind that the rooftop terrace is situated on the fifth floor and you cannot take the elevator up, so this might not be the best place to go when you show your grandparents around. In that case, the bar at ground level would be your safe bet; it has no outdoor seating, but it is also nice.