In the heart of the oldest part of Amsterdam, within the red light district, several tourists visit every year the Amstelkring museum, a.k.a. Ons' Lieve Heer op Solder and a.k.a. Our Lord in the Attic. One of the oldest museums in Amsterdam, Our Lord in the Attic is an original XVII century home, that lies by the canals and hides a church within. It was built when the Catholics were forbidden to practice their religion in public. Jan Hartman, the house owner, decided to convert the top floors into a church (complete of altars, chapels, confessional and organ) so that masses could be held, during the years of the Alteration. The hidden church served as parish for the city center during at least two centuries.