The Town Fortification can be visited
City Wall Ahrweiler-Niedertor

The Ahrweiler-Niedertor town fortification is an example of medieval defensive architecture in Rhineland-Palatinate. As part of the Ahrweiler town fortifications, which are still almost completely preserved today, the Niedertor is part of the city's history.
History+
The origins of the Ahrweiler town fortifications date back to the mid-13th century, with the first written mentions of the moat in 1261. The town gates, including the Niedertor, are documented from 1297, and the town wall itself from 1298. The entire complex, now protected as a cultural monument, once comprised an 1800-meter-long wall and four town gates. The town moat, divided into four sections (Jeuchengraben, Weilergraben, Faulengraben, and Bitzengraben), was fed by the mill pond and could be flooded in times of war.
Image: http://commons.wikimedia.org/wiki/File:Ahrweiler,_Niedertor,_2011-10_CN-01.jpg
Location: 50.5438, 7.0988