Exchange 2010 SP3 - Online Archive Database Removal

Hi,

I want to remove online archive database from my server to gain disk space. I have taken all the users out form the database already except for a "System Mailbox{av09777761ba16" which still shows up when I check though Exchange Management Shell. I don't see it in GUI at all.  From the Shell it does not show me the complete numbers in the bracket.

First of all what is this system mailbox? and is it safe to remove it?

How should I remove the mailbox without seeing the full path in shell?

Thanks,