There's a possibility you might be thinking of something else, perhaps:
* The Order of the Phoenix's secret headquarters: This location was kept hidden from the Ministry of Magic and was frequently used as a safe haven for Order members.
* The Room of Requirement: This secret room in Hogwarts was used by Dumbledore's Army to practice and store their supplies, which could be considered "hidden" from most of the school.
* The Weasley's secret tunnel to Hogwarts: The Weasley family uses a secret tunnel to travel from the Burrow to Hogwarts. This could be considered a hidden passage.
Could you provide more context or information about the parcels you're referring to? This will help me understand your question better.