To locate the Cisco Location ObjectID, perform these steps:
Start adsiedit.msc, found on a DC or in the Cisco Unity \commserver\techtools directory.
If you get an error running it, you might have to register the DLL first. Register adsiedit.dll by running regsvr32.exe c:\adsi\adsiedit.dll after the c:\winnt\system32 command prompt.
Once adsiedit is open, right click on the ADSI Edit (the top level) and select Connect To. This should open up a connection window.
Press the Advanced button and select the Global Catalog for the protocol. Press OK to close that window, and select OK again on the connection screen. This should add a new entry at the bottom named "Domain NC[ ]".
Right click on that new object, select New > Query. This opens a new query screen.
Enter any name for Root of Search, and hit the Browse button. Typically, you would want to start from the root (thus the name Root Search).