The Rockpile, Hue is one of the favorite tourist destinations in this Vietnamese city. Generally people heading for Hue, or broadly speaking for Vietnam would look for the past of this land, which consisted in the reigns of several emperors as well as the recent socio-political topsy-turvy in the last half of the previous century. Nothing to do with the emperors' eras, The Rockpile is basically related to the Vietnam War.
This is a tall rocky mountain that the marines used as a helicopter/artillery base. It's so hard to get to without a helicopter, it was never overrun.
The Rockpile is located in northern Quang Tri Province in Hue. It is regarded to be the first stop north of Hue on your tour to this Vietnamese city. This particular place was used as the famous listening post and a guide port for bombers during the Vietnam War. From here the US troops were helicoptered in and out.
The Rockpile was also an artillery base during that time. This was a weaponry with a huge array of big guns, including 175 long Toms, 8-inchers on tracks, 105s and 155s.
During your Hue visit, you must see this place.