Nichols Arboretum (affectionately known as 'The Arb' by locals) is operated by the University of Michigan, which for administrative purposes considers it together with the Matthaei Botanical Gardens to comprise a single unit (MBGNA). The two lie several miles apart, and most visitors consider the two nature areas to be quite distinct in what they offer. Nichols Arboretum occupies some prime riverfront along the Huron River, starting just east of the Medical Center campus. Except for the very eastern part, where a tall grass prairie restoration is underway, Dow Prairie, the terrain is steep and mostly wooded. Along the margins of the woods and in the open areas (often referred to as valleys or glens) there are many trees labelled with common and binomial names. Trees both native to North America and imported from around the world can be found, many of them as large, mature specimens, dating to the 1920's - 1950's. Apart from various plantings of rhododenron and azaleas, and a few flower beds that surround them, the only flower garden in the Arboretum is a world class peony garden. Wildflowers abound in the woods and on the prairie, however. Hiking or jogging trails criss-cross both the wooded and open areas. There is no officially approved river access for boaters along the river in the Arboretum. Swans, geese, and ducks nest along it as a consequence.
For a nice map of the Arboretum in pdf form, see http://www.lsa.umich.edu/mbg/files/ArbGuide.pdf