More of a thought exercise really but thinking about it the other day, I realized that downtown Raleigh has so few blocks that are 100% car-free. With Nash, Moore, and Capitol Square being the obvious, I could only find two of them.
The best example is the eastern side of 200 Fayetteville. Historic structures plus the buildings around Market and Exchange plaza have created a pedestrian-only block, 100% throughout. One caveat could be that the old bank building at 227 Fayetteville has an underground tunnel to the parking deck to the east (GoRaleigh Station) so you could nix this block because of that.
The other one I think is 100% car-free is the future site of rusBUS which will obviously change in the future.
Although, as I was looking around, a single car in an alley invalidates my thinking!