The Northfield Mountain Recreation and Environmental Center is a Pump Storage Power Facility.
One of the many outdoor recreational oportunities offered is mountain biking and in the winter fat biking.
The center does do some grooming in the winter, but it's sporadic. Updates on trail conditions are posted here.
Riding here is a lot of fun. The trails range from easy to quite challenging. In all there are over 25 miles of trails.
The trails are open to class-1 e-MTBs
A great description of Northfield Mountain is on this Trailforks page.