Please post a picture of the site and tell about this area of the trail. It would be awesome if you linked the post of your opencache and the plaque at www.facebook.com/wehrnaturecenter.
Whitnall Park includes Wehr Nature Center http://goo.gl/KFBqt
(hours 8 am - 4:30 pm) and Boerner Botanical Gardens (grounds open till dusk through October 7.) There is a fee for these areas. Geocaching is recommended in the other areas of the park. Parking in designated areas. Contact naturer center for more information. 414-425-8550.