This airport is quite famous because John Travolta's house is located on its grounds. This is were he parks his own Boeing 707.
The scenery is for FSX only, and is offered as a free download for all Chicago O'Hare customers, it will automatically run registered if the users has bought O'Hare, otherwise it will only run in Trial Mode. However, it's not possible to purchase Greystone separately.
Regardless of its small size, the scenery has been made just like any payware product: it has an hi-resolution 26 cm/pixel photo-realistic background with autogen that blends nicely with the surrounding area, several animations of birds, cars and people, AFCAD with a parking stand big enough for a jumbo jet in front of the house and, of course, John Travolta's house fully modeled and textured in 3D. Runway texture has been enhanced too with skid markings.
This release will hopefully be the beginning of a new offering from FSDreamTeam: small free "bonus" products, offered to all existing customers as a token of appreciation for their support.
To get the scenery, head to FSDreamTeam forum: