While we are pondering what lies in the mountains along the modern Virginia-Kentuky state line, we certainly ought not omit mention of the deepest gorge east of the Mississippi River: the Breaks. This gorge is formed by the Russell Fork "breaking" its way through Pine Mountain. The resulting canyon is called by some "The Grand Canyon of the South." While quite beautiful, this natural site is, of course, simply not on the scale of such gorges in the western United States. Still, it is well worth a visit if you are in the area!
A view of the Breaks from Dickenson County, Virginia.
It is said that the famous Daniel Boone discovered this gap, or break, in Pine Mountain in 1767AD. This was, and is, the only such gap in the mountain for a stretch of 125 miles. Its remote location and narrow sides meant, however, that it never hosted the traffic that Cumberland Gap to the south would.
Today the Breaks are part of "Breaks Interstate Park" that is so-called owing to its being in both the Commonwealth of Virginia and of Kentucky. Here is the web-site for this part: