It's an 18 mile loop around Arlington, Winchester and Woburn with 1800ft of climbing.....a fair amount is above 10%. It's a good way to get a quick workout if you are in the area.
NEBC Wednesday Night Hill Ride at Bikely.com
Nun, that is a killer ride that is on my list, although i have ridden some of those hills before. Not for the faint of heart...