The gate was built between 1471 and 1492 in the current structure.

It’s characterized by an arch and ashlar jambs and it’s defended by two towers, plus one on the side.

At the time was a fortificat bastion in the area where the east walls of the city of Narni did a corner with the side which goes up until the Fortress built by the Cardinal Egidio Albornoz a little over a century earlier. 

Inside of the towers, fitted with fire vent slots, there were semicircular rooms which were used by the soldiers of the garrison that defended it. 

In 1846, on the actualization of a road project which included the actual Piazza Garibaldi, and completed the axis with the Romana Gate, Porta Ternana was elevated of seven romans feet. 

In 1940 circa some stones, which were placed not far away, were uprooted to permit the passage of the heavy vehicles.  

On the top of the door there is the coat of arms with the griffin, symbol of the town of Narni.