CHICAGO-The Texas Medical Center in Houston is considered the country's granddaddy of all healthcare facility concentrations. And why wouldn't this be the case? The area just outside of Houston's downtown has a total of 37 million square feet inside numerous hospitals, medical office buildings, clinics and research facilities.

The US is home to some other big medical concentrations as well, including San Antonio's South Texas Medical Center and Boston's Longwood Medical Area. However, one of the under-the-radar medical districts is the Illinois Medical District.

Located just a couple of miles from downtown, IMD is a 560-acre area that includes 40 healthcare-related facilities including four major hospitals – University of Illinois Health & Sciences System, Rush University Medical Center, Jesse Brown VA Medical Center and John H. Stroger Jr. Hospital of Cook County. Also on site are medical research labs, a biotechnology business incubator, universities and an area of developable land.