That video is interesting both for what is says and what it doesn't say. (full disclosure: I worked for 30 years, until my retirement last fall, as an attorney for the TN Dept of Environment and Conservation. TDEC and the TN Wildlife Resources Agency have not always played well with each other.) This video is from the program, Tennessee's Wild Side, produced by, or with the support of TWRA. See: http://www.tn.gov/twra/infoed.html
The forest this video has been named the Hill Forest, for the man Hoyt G. Hill, who owned it for much of the 20th century and contrary to what he did with other land he owned, never cut the trees. It was saved from a developer when the Friends of Warner Parks purchased it, when Warner Bass, who speaks near the end of the video, was president of the group. Sandy Bivens of the Warner Park Nature Center also speaks on the video. The plan is for the property to be turned over to Metro Nashville to be made part of the Warner Parks, although I understand that has not yet happened. TDEC working with Metro Nashville worked to pass a bill in the Tennessee General Assembly that made the Hill Forest a designated state natural area, which gives the property the highest level of protection available under Tennessee law. More protected than a state park, for example, on which the state could decide to build a golf course, other recreational facility, or an inn. See http://www.state.tn.us/environment/natural-areas/natural-areas/hillforest/
As that last link says the total acreage of the Hill Forest is 225 acres, although I believe not all of that is the "old growth" area. The video states that the area is across the highway from the park. That is almost accurate. Immediately across Highway 100 from Edwin Warner is a tract of land much of which has been pasture and some was logged. This was purchased for the Warner Parks prior to the Hill Forest. The Hill Forest tract is past it and goes up to HIghway 70 at the top of nine mile hill. There is a link to a map on that last link, as well. The Hill Forest is not currently open to the public, however, the Warner Parks do have guided walks on the property from time to time. I went on one about 6 weeks ago. Watch the calendar of their activities (at: http://www.nashville.gov/Parks-and-Recreation/Nature-Centers-and-Natural-Areas/Warner-Park-Nature-Center.aspx) for another opportunity.