Chanhassen is home to the Seminary Fen which contains one of the rarest types of wetland in the United States, a calcareous fen. Calcareous fens are characterized by a substrate of peat and are dependent on a constant supply of cold, oxygen poor groundwater rich in calcium and magnesium bicarbonates. They have special protection under Minnesota state law and may not be drained, filled or otherwise altered or degraded.
The Seminary Fen is also a Scientific Natural Area. This means there are no trails or other facilities, but the public is welcome to explore by foot, snowshoes, or skis. Parking is located from downtown Chaska 2 miles East on Chaska Blvd. Camping, picnicking and swimming are not allowed on SNAs. Bringing water or snacks on site is allowed.