VIM Fitness has two locations less than 1 mile from NGIN Workplace, and membership grants you access to both locations. They also boast "the most group exercise classes of any gym in Cambridge".
Members of NGIN Workplace receive a $10 discount on Monthly Membership at VIM Fitness. Get even more bang for your buck by signing up for VIM's Yearly Membership - you'll save $125 compared to the original price!
To receive the discount, just head over to one of their nearby facilities and mention you are coming from NGIN, and in the "Reference" section of their forms include "NGIN Workplace".