The Alteration and the making of modern Amsterdam

In 1578, a religious and political upheaval known as the Alteratie transformed Amsterdam from a Catholic-controlled town into a Protestant stronghold. But what followed was not repression — it was an extraordinary experiment in tolerance. As Eduard Janssen explains: “Due to its relative tolerance and freedom, Amsterdam became a haven for many immigrants.”

Religious refugees, merchants, scholars, and craftspeople arrived from across Europe, drawn by the promise that they could live and work in relative peace. Jewish communities became so integral to the city that Amsterdam earned the nickname Mokum, from the Hebrew Makom, meaning “place” — a testament to how deeply these communities shaped the city’s identity.

Seventy years after the Alteration, the Peace of Münster and the Treaty of Westphalia in 1648 cemented Amsterdam’s position. These agreements did not just end wars — they laid the foundation for the political map of Europe and strengthened Amsterdam as an international trade centre. The city’s openness was not idealism. It was strategy, and it worked.

Today, the same instinct — welcoming talent, fostering exchange, protecting civic freedom — still runs through Amsterdam’s institutions and culture. The Alteration happened nearly 450 years ago, but its consequences are visible on every canal and in every conversation about what makes this city different.

Did you know

Hidden Catholic churches — schuilkerken — operated openly within ordinary canal houses for two centuries after the Alteration. One built in 1663 on the Oudezijds Voorburgwal, behind a plain façade, seated 150 people, had a functioning altar and organ, and was known to the authorities — but tolerated. It still exists: the Museum Ons' Lieve Heer op Solder, "Our Lord in the Attic." The bargain of Amsterdam's tolerance made visible in brick and timber.

Explore Amsterdam with insight

Join Eduard for a private tour and discover the stories behind the city.

Get the Most out of Your Visit