Europe, I learned, was introduced to cocoa beans when Spanish explorers brought them back from what is now Mexico in the late 16th century. They reached Belgium about 100 years later. When King Leopold II colonized the African Congo from 1885 to 1908, partly for the cocoa crops, the resulting genocide was a dark moment in the country’s history. It is also when Belgian chocolate started earning its formidable reputation.

Outside the museum, I dodged the camera-wielding tour groups gathered before the magnificent Grand’Place, with its 15th-century Town Hall and rows of guild houses, and walked down narrow streets lined with friteries and waffle stands. Soon the cavalcade of chocolatiers continued in the Galerie de la Reine. La Belgique Gourmand, Corné and the original Neuhaus were at home under the soaring glass ceilings of this graceful fin-de-siècle shopping arcade. But as big business as those Belgian brands are, none are national gems the way Mary is.

The 92-year-old chocolatier is a favorite of the Belgian royal family, and with its rows of caramel, marzipan, chocolate mousse, ganache and cream-filled pralines, it was easy to see why. Mary makes small batches of chocolates, so they don’t have to be stored, which is when they lose their flavor. Buzzing from the caramelized hazelnut pralines the saleswoman had offered as a sample, I found myself leaving $70 lighter, but two boxes of pralines and several chocolate bars richer.

Compelled to dig deeper into the chocolate of Brussels, and the city itself, I ambled down the crooked Rue des Bouchers, avoiding eye contact with waiters trying to lure me into their cafes for buckets of mussels; past the big, blocky Bourse where workers in loosened ties ate sandwiches; into St.-Géry, where the canals once used for transporting building materials are now filled in and home to seafood restaurants. I veered left and found the big shop windows of Ste. Catherine, an area popular with artists and fashionistas.

I was on Rue Antoine Dansaert, put on the map by the radical Antwerp Six, the designers who established Belgian fashion in the 1980s. Today the neighborhood is still a bastion of cool with boutiques like Stijl, which features the likes of Ann Demeulemeester, Raf Simons and Dries Van Noten. In recent years, foreign brands have infiltrated, including our very own Marc Jacobs.

Any chic shopping district worth its salt has fantastic places to eat, and I found mine in Selecto, a bistro that opened in August. Drawn by the vintage ad posters that were splashed across the smart black and white interior, I ordered cod served atop polenta, just the sustenance I needed before heading to the lesser-known neighborhood of Ixelles.

The 30-minute walk across town felt like a tour of different cities. I passed comic murals and quirky second-hand shops in the gentrifying Marolles neighborhood. I gazed up at the medieval Porte de Hal, the last remains of the city walls. After crossing the wide, looping Boulevard de Waterloo, the landscape became hillier and the architecture uniform. I was in St.-Gilles, a bonanza of Art Nouveau.