This is the Virginia (eastern) portal of Pine Mountain tunnel, blasted out in 1947 and sealed up, at least from the Kentucky side, in 1958.  It’s just off Highway 667 above Almira, if you’re coming out of Pound.  The access is at the “Red Fox Trail” sign, but don’t expect an easy way in.  The railbed is heavily overgrown with high marsh grass and there was a lot of marshy goop around.  We leaped, gazelle-like, across a creek and climbed up to the top of the cut and pushed our way through trees, some briars, and other of Nature’s finest obstacles, to where we could get a fairly clear view of the portal.  You actually can’t see it in either of these pictures, but on that light-colored band across the top of the portal is written “1947 PINE MOUNTAIN TUNNEL’.
The Chesapeake and Ohio railroad created this tunnel in order to open up a vast (300 million tons!) coal field just east of Pound VA.  A big thank you to Chris Balthis for providing me some rich research material on this nearly forgotten tunnel.