Mall of America Spring
Old maps of the Fort Snelling Military Reservation show a feature called Big Spring, draining to Long Meadow Lake.  Prospecting in this area years ago, very close to the Mall of America, I was able to relocate the spring.  The springs in this part of the Minnesota River valley are distinctive, being found at the heads of ravines in which no bedrock is visible.  They are especially easy to locate after the leaves have fallen--just look for the willow trees and watercress, which tend to stand out at that time because of their greeness.  Mound Springs Park has some excellent examples.
Big Spring, at head of ravine.  Under the rock at the very springhead I saw a snake staring out at me.  Some sort of guardian?