The 26-meter-high round tower made of rubble masonry formerly marked the southeast corner of the city fortifications. The entrance to the tower was situated high above the battlements of the city wall and was only accessible via a ladder. On the side facing the attack, there is a sandstone relief high up depicting Archbishop Johann II of Nassau kneeling before the crucifix, who completed the tower in 1411.

The Powder Tower is owned by the Lahnstein Brewery. It also houses the local carnival guard "Närrische Turmgarde Lahnstein" in its club room.