In the location's words:

With around 8,500 members, St. Peter's is Bremen's largest parish.

St. Peter's Cathedral can be visited free of charge during opening hours.
Church services and parish events may make it necessary to close the cathedral.
We endeavor to keep the cathedral open as far as possible and ask for your understanding,
should it not be possible to open for the above reasons.

Die Öffnungszeiten gelten für den Dom.
Domkanzlei, Turmbesteigung und Bleikeller haben andere Öffnungszeiten.