Due to a new High Administrative Court sentence renting an apartment for touristic purpose can be more risky than in the past.
The authorities can now direct / over-rule a landlord that an apartment will be used in the future again as regular housing space for locals instead of being a tourist apartment. Remark: Nearly 100% of apartments in multi-apartment houses in Berlin are originally planned for housing - so no surprise for landlords; just an improved way to force them not to act against communities.
For tourist this means that between booking and arrival it is possible that the apartment is no longer available for that purpose. In extreme cases guests can end up without accomodation although booking was successful and pre-paid - already happened in context of protecting housing spaces from abuse.
I do not know what it means for Hamburg, Cologne and Munich.
The court sentence can get under revision.