A nice and centrally-located state park just south of Lake Mille Lacs. It is open all year round - in the winter they offer some groomed CC ski trails. I would recommend visiting to tower as well. It offers a good view of the surrounding part and some of the lake. Though, it does close during the winter months. The trail center is open and free to use (obviously with a park pass). There is a warm fireplace which is very nice during the cold winter months. Additionally there are some tables inside the building for use, plus a free bathroom.
There are many trails of various uses, but some can get wet in the spring/summer months, so definitely be aware of that.
The only negative is that it can get crazy buggy in the moist and warm months of spring/summer. It is nice to travel back during the winter to experience the freedom from the bugs.
The entrance is nicely signed coming from HWY169. Very easy to get to. Overall a very nice park and I would definitely recommend a visit.