STATE PLAZA LOOP
~9 miles from/to PE Building

*Distances are approximate and assume you begin and finish at the PE building.

1.  Take Western Avenue EAST (the red dots/arrows) [~3 miles]
2.  Adjacent to Washington Park, Western forks with State Street, go RIGHT to take State Street. [~1 mile]
3.  Turn right to run ACROSS the mall of the State Plaza, coming out on Madison Street. [~ 1/4 mile]
4.  Turn right on Madison and continue until it merges with Western Avenue. [~2 miles]
5.  Return to campus via Western Avenue. [~2 miles]

This is a fairly easy loop.  The return up Madison begins with a gradual uphill, but nothing excessive. 
Additional miles are possible by running in Washington Park,  as well as adding on variants of the Manning loop, etc.