Rennes' actual population is more like 220k, but that still is enough to be number 10 or 11 in France. It's the urban area that comes to around 360k, though there also is the metropolitan area with around 750k. But the city itself is 220k. By any of these means, it's not a megacity, but there are many, many much, much tinier places in the region, regardless of how you define "region".