Most roundabouts in a roundabout

The most roundabouts in a roundabout is 6, and was achieved by the Plough Roundabout in Hemel Hempstead, UK, in 1973.

With an almost infinite number of possible routes the "Plough Roundabout" is the world's most complex roundabout. It comprises of six smaller roundabouts around the circumference of a larger roundabout, it is possible to travel both directions around the larger roundabout to exit via the driver's chosen road. Each of the smaller roundabouts has three entry and three exit lanes, providing both choice and confusion for any driver attempting to traverse the roundabout without experience. The design of having mini-roundabouts in a roundabout was invented by Frank Blackmore of the Transport and Road Research Laboratory.