For a real nightmare roundabout, the winner has to be Place Charles de Gaulle around the Arc de Triumph in Paris[0].
It is about 8 lanes across, with no lane markings, and with vehicles entering the roundabout from one of 12 junctions having right-of-way.
I'm not sure what was happening on the day the Google maps aerial photo was taken, as it unfortunately it doesn't show the chaos that normally ensues.
[0] https://www.google.com/maps/place/Arc+de+Triomphe/@48.873766...