Backups are stored in a safe or in a secure data centre

If there is no geographical distance, ensure that the storage is in a physically secure place such as a high-quality safe (anti-fire, anti-flood, anti-burglary) or a sufficiently secured room, both of which give the best guarantee for restoring data.

Back-up media need to be reasonably resistant to theft, fires, floods, etc. Storing back-ups in a safe, or another sufficiently secure place, means protecting yourself against these eventualities.