By 1965, the European Economic Community's executive — the precursor of today's Commission — had 3,200 staff scattered across eight different cramped buildings near the Schuman Roundabout in Brussels. The Belgian government saw an opportunity. Other countries were lobbying to host European institutions; Strasbourg already had the Parliament, Luxembourg had the Court of Justice. Belgium offered to build a grand custom headquarters at its own expense if the Commission would commit to staying. Walter Hallstein, the cautious German jurist who served as the Commission's first president, said yes, sort of. The land Belgium offered was occupied by a three-century-old convent and its girls' boarding school, run by an order known as the Ladies of Berlaymont. They sold their site, moved south to Waterloo, and the name moved with them onto the building that replaced their convent.

The architect was Lucien De Vestel, working with Jean Gilson and engineer Joris Schmidt. They drew their inspiration explicitly from the cruciform UNESCO headquarters Marcel Breuer, Pier Luigi Nervi, and Bernard Zehrfuss had built in Paris in 1958. The Berlaymont's four unequal wings spread from a central core, supported by piles, with a 40-metre concrete spine running through each wing and a glass facade hung from suspended steel beams. The top floor — the thirteenth — was unique: suspended from the upper beams rather than supported from below, which meant the level beneath it could stand free of internal columns. The whole structure was meant to suggest light and transparency, two qualities Cold War-era institutional architecture often promised and rarely delivered. The cross shape became iconic almost immediately; by the 1970s, you could tell a story about European government just by drawing it.

Then came the inspection. In 1990, building surveyors discovered that the structural fireproofing sprayed onto the Berlaymont's columns and beams during construction was loose asbestos — already shedding fibres into the air the commissioners breathed. The civil servants' trade unions made the issue impossible to ignore. By the end of 1991, the entire Commission had been moved out. Commissioners and their cabinets went to the rapidly completed Breydel building; other departments scattered to eleven different buildings across Brussels at a cost to the Belgian state of 14.8 million euros a year. Removing the asbestos took until 1999. Renovating the gutted shell to modern standards — better natural light, individual office heating, double-glazed mobile screens on the facade that adjusted to sunlight and acted as a sound barrier against the traffic on Rue de la Loi — took another five. The bills kept arriving. By the time the building reopened in stages from July 2004, it had been deserted for thirteen years.

The Berlaymont houses the office of the European Commission's president on the thirteenth floor, alongside the College of Commissioners' boardroom, the meeting room for the weekly cabinet known as the Hebdo, and a small restaurant called La Convivialite. Ursula von der Leyen became the first Commission president to actually sleep in the building — she keeps a small private apartment next to her main office on the thirteenth floor, which she occupied when she took office in late 2019. The arrangement spares her the commute from her family home in Germany and lets her be at her desk minutes after waking. Six Directorates-General — Human Resources and Security, the Secretariat-General, the Legal Service, Communication, the European Political Strategy Centre, and the Brussels Office of Infrastructure and Logistics — also work in the building. The remaining staff of the Commission, totalling some 30,000 civil servants, work in around sixty other buildings across Brussels. The Berlaymont is the symbol; the work happens everywhere.

On 18 May 2009 a fire broke out in the Berlaymont's basement archives, spreading through a cabling shaft to the upper floors. The building was evacuated. There were no casualties, but the incident exposed something unsettling: the renovated Berlaymont has no fire sprinkler system anywhere except in its garage. Periodically, journalists and architects have wondered out loud whether the cross-shaped tower is really the right symbol for the European Union in the twenty-first century — too inflexible, too Cold War, too small for a Commission that has tripled in size since the building was conceived. New towers have risen around it: the Justus Lipsius and the Europa hosting the Council, the Charlemagne next door. But the Berlaymont remains the address. When journalists film a stand-up about a European policy announcement, the cruciform glass facade behind them is the European Commission, the way the West Wing is the American presidency. The building that almost killed its tenants with asbestos and almost bankrupted its landlord with delays now appears in stock footage of European democracy every single day.