Archive has died and gone to heaven

Having run out of room, and resorting to guesswork about what to delete, I copied a set of archive folders to my local drive and then deleted them from the MIB server (Ubuntu 14 on DigitalOcean).
Subsequently, I discovered I could solve my problem by deleting backups from the server, and so now I have backups on my local drive and room enough on the server that everything is functioning normally.
Everything, that is, except archiving.
I obviously don’t know where I should be restoring those Archive folders to on my server. My RoundCube screen shows an Archive folder available, but when I archive a message, it apparently pines for the fjords and joins the Choir Invisible. So far I’ve only done this to sacrificial messages, but at some point I’ll want to archive important ones.
Any suggestions about where I should restore those archive folders to would be gratefully appreciated.