The striking defence system was built in 1568 in anticipation of an attack by the Spanish Armada near Duncannon on a headland. But the Armada never made it to Ireland. Luckily! In this way the facility remained completely undamaged and it looks as if it is still watching over the bay today.
The path leads into the interior via a wooden bridge spanning the moat. Inside the complex, which still looks like a barrack today, there is a museum where visitors can inform themselves about the history of Duncannon Fort.