IARC is the Illinois Accelerator Research Center. It is part of what used to be the CDF experiment building.
See the Fermilab Site Map. IARC is located on this map at the red dot labeled “CDF”.
Here is the site map marked up with directions from the East (Batavia Road) entrance (green) and from the West (Pine Street) entrance (red):
Here is a satellite view (from Google Maps) of IARC:
The GPS Coordinates of the entrance to IARC are: 41.840857, -88.2519502