The site is called the Galgenberg, which translates literally as Gallows Mount. In the Middle Ages, this hill between Brussels' upper and lower town was where the city hanged its convicted criminals, a piece of geography too useful not to use again. The old neoclassical courthouse, built between 1818 and 1823 by the architect Verly on the site of a former Jesuit church, started falling apart almost immediately. By 1837 there were calls for a replacement. A reconstruction project in the same location was estimated at three million Belgian francs and was abandoned. The Leopold Quarter was proposed and rejected. Another scheme in 1846 went nowhere. Belgium spent twenty years arguing about where to build a new Palace of Justice before anyone agreed on a hill. The Galgenberg won. The criminals had been moved on long before, but the name stuck.

Joseph Poelaert was the municipal architect of Brussels, already known for the Congress Column and the Church of St. Catherine. In 1861, Minister of Justice Victor Tesch handed him the commission for the new courthouse. Poelaert went to Paris to work in peace, far from Brussels' politics, and came back with a design that nobody had asked for and nobody quite understood. His Palace of Justice would be eclectic Greco-Roman, drawing on classicism but invented from scratch. It would cover 26,006 square metres of ground - larger than St. Peter's in Rome. Its central dome would rise above the Brussels skyline visible from every approach. The first stone was laid on 31 October 1866. The cost would eventually reach about 50 million Belgian francs, a sum that produced its own political crises. Poelaert never saw it finished. He died on 3 November 1879, four years before the inauguration, and his successor Joseph Joachim Benoit took the project to completion.

To build something this large on the Galgenberg, the city had to evict the people already living there. The Marolles, the working-class neighbourhood below the hill, lost houses, streets, and entire blocks to the construction. Families who had lived there for generations were displaced; their world was demolished so that the law could have a bigger atrium. The neighbourhood's bitterness toward Poelaert became permanent and idiomatic. In Brusseleer, the local dialect, the phrase schieven architek - crooked architect - became a serious insult, born from this displacement and aimed by extension at anyone perceived to have wronged ordinary people through grand designs they could not push back against. The phrase still exists. Poelaert's posthumous reputation in Brussels carries that asterisk: the man who built the largest building in nineteenth-century Europe, and the man whose name his neighbours used as a curse. King Leopold II inaugurated the finished building on 15 October 1883 and showed almost no interest in it. It is not counted as part of his architectural legacy, despite being inaugurated during his reign.

On the eve of the liberation of Brussels in September 1944, German troops, retreating, set fire to the Palace of Justice. The aim was to destroy the building and the legal records it contained. The cupola collapsed. Two months later, a V-1 flying bomb exploded in the nearby Rue des Minimes and finished the damage. When restoration began in 1947, the architects took the opportunity to fix something everyone had quietly disliked about the original dome - its somewhat squat profile - and rebuilt it 2.5 metres higher than Poelaert's original. The new dome, gilded and lifted, became the Brussels skyline silhouette that still photographs do. There is also a persistent story that Adolf Hitler admired the building, and that Albert Speer, his architect, was dispatched to Brussels in 1940 to study it. Speer admitted as much in his memoirs. The Palace of Justice in Lima, Peru, which houses the Supreme Court of Peru, is also based on Poelaert's design, dome removed and dimensions reduced.

Renovations on the building began in 1984. They are still going. Bricks crumble. Ceilings collapse. In 2018 a chunk of plaster fell, and Jean de Codt, the first president of the Court of Cassation - the most senior judge in Belgium - went on the radio to demand additional funding for a building whose state, he warned, was a danger to the people who worked inside. Courts have moved out. The Court of Cassation, the Court of Assizes, the Court of Appeal, and the Tribunal of First Instance still meet here, but many other jurisdictions have given up and relocated to office buildings elsewhere in Brussels, on the grounds that Poelaert's vast spaces do not meet modern requirements for workspace, security, or accessibility. The Place Poelaert in front of the building - the largest square in Brussels at 155 metres across - functions mostly as a traffic roundabout, a vast unpedestrian space ill-suited to the people it was meant to grace. The view from the square is still extraordinary: across the lower city you can see the spire of the Town Hall on the Grand-Place, and on clear days the Atomium far to the north. From the square you can also take the Poelaert Elevators down to the Marolles, the neighbourhood the building was built on top of - a small mechanical apology, opened in 2002, that connects what nineteenth-century power separated.