Amsterdam went over to the Reformation in 1578, and the Dutch Republic that followed made a distinction that was unusual for its time: it guaranteed liberty of conscience while granting only the Reformed church the right to worship in public. Catholics, Lutherans, Mennonites and Remonstrants therefore worshipped in buildings that did not look like churches from the street. Ons Lieve Heer op Solder, our Lord in the attic, is a merchant house whose upper floors were opened up into a full church with galleries and an altar, and it survives as a museum. Everyone knew such places existed, and the authorities were paid to leave them alone.
That was toleration on practical terms rather than on principle, and its limits were real. The Reformed church itself split badly over predestination, and the Synod of Dort in 1618 and 1619 condemned the Remonstrant position, deposed its ministers and exiled some of them; a leading statesman was executed in the same quarrel. Amsterdam's printers meanwhile produced books that could not legally appear elsewhere in Europe, in Hebrew, Latin, French and English, which made the city the place where a great deal of religious argument was physically manufactured.
The city's Jewish population, Portuguese and Ashkenazi together, was around eighty thousand before 1940. Some three quarters of Dutch Jews were murdered in the Holocaust, the highest proportion in western Europe, and in February 1941 Amsterdam dockers and transport workers struck in protest against the first round ups, which is the only general strike anywhere in occupied Europe called against the persecution of Jews.