A viral video on social media has brought to light the fascinating story of the Coudenberg Palace, once the most impressive royal residence in Europe. Destroyed by a fire in 1731, the palace was forgotten for centuries, and today visitors can explore its underground corridors and discover the secrets of one of Belgium’s most mysterious sites.

(Staff: Belgium / History & Heritage)

Beneath the elegant cobblestones of Brussels’ Royal Square, just a few metres below the feet of passers-by, lies one of Belgium’s best-kept secrets: the Coudenberg Palace. Once the political heart of Europe, the favourite residence of Emperor Charles V and the place where important pages of continental history were written, it is now an underground labyrinth of cellars, corridors and ceremonial halls waiting to be rediscovered.

“Belgium’s most secret castle”

A video that went viral on social media, shared by hundreds of thousands of people, has brought this hidden treasure back into the public eye. “C’est LE chateau le plus secret de Belgique !” – the title accompanying the footage filmed inside the palace – reflects the creator’s enthusiasm.

The palace that disappeared underground

The story of Coudenberg begins in the 11th century, when a first fortified castle was built on this hill. Over the centuries, the castle was transformed into a grand palace, becoming the residence of the Dukes of Brabant and then of Emperor Charles V. At its peak in the 16th century, it was considered one of the most beautiful and largest palaces in Europe.

It all ended in a single night: 3 February 1731. A devastating fire almost entirely destroyed the palace. Instead of being rebuilt, the ruins were covered with a thick layer of earth, and above them the new royal quarter was built, with the Royal Square and the Royal Palace. The Coudenberg Palace disappeared, and its memory was gradually forgotten.

Rediscovery of the underground city

It was not until the 1950s, during construction works, that the first vestiges were rediscovered. Systematic archaeological excavations, begun in 1995, uncovered an impressive part of the palace: the cellars, the underground corridors, the foundations and even a cobbled street that led to the former stables.

Today, visitors can explore this underground labyrinth via a multimedia trail called “UNDER-GROUND”. With the help of an audio guide and 3D reconstructions, time-travellers can rediscover the sumptuous atmosphere of the palace, visit the dungeons, and listen to the legends associated with this place. The new exhibition, open until March 2027, reveals new secrets of the palace and offers a unique perspective on court life in past centuries.

What can you see today?

Among the most impressive remains are:

• The Church of St James, whose foundations are still visible
• The palace cellars, which served as storage rooms and prisons
• The cobbled street that led to the stables and the courtiers’ houses
• The hot-air heating system, a remarkable technical invention for its time

Conclusion