Is Grand Cru the highest?

Excuse me, but I'm curious about something. In the context of wine classification, particularly with regards to Burgundy, is "Grand Cru" indeed the pinnacle of quality? Or is there perhaps a higher tier that I'm unaware of? I've always been fascinated by the intricate hierarchy of wine appellations and would appreciate any clarification you could offer on this matter. Thank you in advance for your insights.