maintains eleven public golf courses. There are six nature centers used for programming and education, five campgrounds, and three swimming centers. In 2016, a tree-top zipline course was opened in west Cook County's Bemis Woods. National sites The Ned Brown Forest Preserve contains Busse Woods, a National Natural Landmark. The District also administers the Chicago Portage National Historic Site. In addition, the District's Red Gate Woods was the war-time home of the Manhattan Project's first nuclear facility. Conservation Biologists with the district monitor the health of area wild life, lands, and water. This includes monitoring such populations as the number of fish in area rivers, and the return in the 21st century after a century of absence of such apex predators as the river otter. Twenty-two sections of district land, which contain high quality conservation resources, have been designated as Illinois Nature Preserves allowing greater management and protection. The International Dark-Sky Association (IDA) conservation program designated the Forest District's Palos Preserves an Urban Night Sky Place. After review, the IDA determined that within the context of its substantial urban setting, the preserve's "planning and design actively promote an authentic nighttime experience in the midst of significant artificial light." Trail systems There are thirteen trail systems within the preserve district, they are the: Arie Crown Forest trail system Burnham Greenway trail system Busse Woods bicycle trail Centennial and I&M Canal trail system Deer Grove trail system Des Plaines River Trail system North Branch Trail system Palos Trail system Poplar Creek trail system Sag Valley trail system Salt Creek trail system Thorn Creek trail system Tinley Creek trail system Facilities by region Region 1: Northwest Cook County Poplar Creek Division Includes: Spring Lake Preserve, Crabtree Preserve, Arthur L. Janura Preserve Activity Areas Barrington Road Pond Beverly Lake Bluff Springs Fen Bode East Bode Lake Crabtree Nature Center Great Egret Family Picnic Area Old Stover Trailhead Penny Road Pond Poplar Creek Bicycle Lot Poplar Creek Equestrian Parking Poplar Creek Model Airplane Flying Field Shoe Factory Road Woods Spring Creek Valley Headwaters Spring Lake Nature Preserve Trail Systems Crabtree Preserve (Paved) Poplar Creek (Paved) Poplar Creek (Unpaved) Spring Lake (Unpaved) Region 2: Northwest Cook County Northwest Division Includes: Deer Grove Preserve, Jens Jensen Preserve, Paul Douglas Preserve, Ned Brown Preserve Activity Areas Baker's Lake Overlook Baker's Lake Younghusband Prairie Busse Forest-Central Busse Forest-North Busse Forest-South Busse Forest-West Busse Forest Elk Pasture Busse Forest Main