The Belle Isle ride is at a pretty casual pace. It's around 16-18mph with lots of chatting—very laid back and easy going. Once it hits Belle Isle, they do a loop around the park and you get a chance to crank it up for a mile or two, then everyone regroups at the Starbucks across Jefferson after a coffee break for the return trip. Huge groups of riders.
It's been fun the times I did it.