The Anna Scripps Whitcomb Conservatory is a greenhouse and botanical garden covering 13 acres located on Belle Isle, just three miles east of downtown Detroit. Designed by noted Detroit architect Albert Kahn, it opened in 1904 and is the nation’s oldest conservatory. It’s available to the public free of charge from 10 AM – 5 PM, every day of the year with a “walk-through time” of 30 minutes.
The conservatory site contains formal perennial gardens, annual flower beds, a rose garden, and lily pond garden and permanent displays of rare flora, including one of the largest municipally owned collections of orchids in the nation (including 600 that were donated by Anna Scripps Whitcomb). The conservatory itself covers more than an acre and features an imposing 85′ high central dome with a total volume of 100,600 cubic feet. The south wing contains tropical plants of economic importance such as bananas, oranges, coffee sugar cane and orchids. The north wing hosts the extensive collections of ferns, cacti and succulents. The show house, remodeled in 1980, features a continuous display of blooming plants.
Their website has a lot more information and photos including this shot of the original structure. You can see the location of the Conservatory on the Absolute Michigan map of Michigan, check out the Belle Isle entry on Wikipedia and view a slideshow of Anna Scripps Whitcomb Conservancy photos in the Absolute Michigan pool on Flickr.