We pick g.root-servers.net, one of the 13 root servers (1), and ask it about grdns-ath.ics.forth.gr and learn that gr is delegated to seven name servers (2), so we ask grdns-de.denic.de where we learn that forth.gr is delegated to seven name servers, including grdns-de.denic.de (3), so we ask that one and get the following answer: