You have to go inside the royal museum of arts (left-hand side of the atrium) to get to the café, which means that there were tons of free tables to sit at when I got there. Definitely a plus, especially after getting out the Jat'Cafe which was like a jungle!
Is all self-service, and, during the right hours, you can get a full meal there, which is really nice. They also always have some handy desserts ready for those who have a sweet tooth. I had a cup of tea, which I really enjoyed, sitting right next to the patio windows with a nice view of the Sablon's steeple and the palace of justice's dome.
The place is a little pricy, which is what is to be expected. Teas and coffees are between €2,80 and €5,50 (the latter being for a double expresso), and the batista is basically a fancy machine, but the staff was really nice (granted, I haven't tasted the coffee so I can't say whether it was any good). The cafe also boasts a number of beers, most of which are around €4,00.
I definitely recommend this place to anyone who wants to sit down for a nice chat with friends in a place that isn't overcrowded (though I expect the story might be different in the summer when the larger tourist crowds come by). read more