Bicycle parking for one month

[marshmallow]

I’ve cycled in Europe frequently but have yet to find the best solution to this problem. Where can I leave my bike for up to a month. Most parking garages are quite expensive. Sometimes, friendly hotels will oblige. Does anyone have other suggestions? Relevant cities include Frankfurt, Berlin, Paris, Athens. Cheers.

[RonK]

I recall reading some years ago about a tourist who parked his bike for up to year for minimal cost. I'm pretty sure it was in Amsterdam. I recall any more detail unfortunately.