Located across the Illinois River from the town of Marseilles, the 510-acre Illini State Park lies along the northern edge of the "Great Falls" of the river, where a drop in streambed gradient creates beautiful roaring rapids. The park itself sits atop an old glacial moraine (elongated ridge-type hill "bulldozed" up by an advancing Pleistocene glacier) and features a dense hardwood forest of oaks and hickories on the ridge tops, sugar maple, black walnut, and white ash on the slopes, and silver maple and cottonwood in the bottoms. Hikers (and cross country skiers in winter) can take the park's Marasottawa Trail which loops from the Sycamore Grove Shelter on the east end of the park up to the Mallard Bay Shelter and Boat Launch on the east end. LaSalle County birders mention this trail as one of the best sites in the county for viewing migrating vireos, warblers, thrushes, and other songbirds in fall.