It was hard for me to pick a favorite, but these two are absolutely gorgeous in my eyes (information/photos taken from the People Mover Web site):
JOE LOUIS ARENA STATION - VOYAGE
CADILLAC CENTER STATION
"A profoundly rich green hue emanates from luminous arches, which are surrounded by Pewabic tiles that had been originally fired for the Stroh Brewery in 1955. The mural is interspersed with tiles depicting Detroit workers, which were originally installed in Detroit's Northern High School in 1926. The bronze plaque of Madame Cadillac entering Detroit after her canoe journey from Quebec is by Carlos Romanelli, dated 1903. It is presently on loan from the Detroit Institute of Arts."
Take a look at the site. What's your favorite piece?
Note: Apparently guided art tours are are available for groups of 10-30 by appointment through the tour season (May-October). Hmmm....may just have to get some folks together to learn about the art/history first hand!