A million visitors a year is a massive overestimate considering the Detroit Zoo 2011 attendance was 1.2 million.

http://www.freep.com/article/20120522/NEWS06/120522025/

DNR expects a million visitors a year to Detroit riverfront discovery center

The Michigan Department of Natural Resources said this morning it anticipates as many as a million visitors a year coming to its planned discovery center to be built in the historic Globe Building on Detroit’s east riverfront.

Features will include a 60-foot climbing wall, an archery range, simulator rides demonstrating kayaking and other water sports, and classrooms to teach schoolchildren and other visitors outdoor safety as well as the science of natural resources and wetlands.