The only roundabout I ever biked was the one around the Arc De Triomphe in Paris on a city bike. I realized when I got there that this is no place for bikes. 12 streets intersect at this roundabout, some of them very busy. The roundabout is about 4 lanes wide and the Arc is in the center so there are busses and cars trying to get to that from every intersecting street. I must have been honked at 50 times in the brief time it took me to go 3/4 of the way around. I'll never do that again.