THE ROMAN CITY WALL
The Roman city wall was almost four kilometres long and had at least nine gates and 19 round towers. Remains of this wall can still be seen in various parts of the city. Recent excavations have proved that the city wall was erected at the end of the 1st century AD. Some of the visible remains are described below.
In front of the western entrance to Cologne Cathedral is an arch from the former northern gateway into CCAA. The foundations of the gate and part of the defensive wall can be seen in the underground garage beneath the open area beside the cathedral and in the excavation area under the cathedral. Of significance, further to the north, are a 32-metre-long section of the wall with the so-called 'Lysolph Tower' and a 90-metre-long section of the curtain wall near the Prussian guardhouse next to the Cologne City Museum. The so-called 'Roman Tower', probably the best-known structure in the ancient defences of the city, marks the northwest corner of CCAA. For centuries, it has drawn the attention of citizens and tourists alike.
The city wall continues on the western side of CCAA. A few metres away from the 'Roman Tower' is the 'Helena Tower' in St-Apern-Strasse. Its height of 10 metres gives a good impression of the defensive strength of these ancient towers, although only the lower portion and the foundations are original.
A 160-metre-long section of the city wall with the remains of a round tower can be seen in the open area between Alexianer-Strasse and Mauritiussteinweg. This leads to the southwest corner of the city wall at Griechenpforte.
The city wall then followed the course of a former river, the Duffesbach, down to the Rhine. Another section, 78 metres long and over 6 metres high, is visible on the level of Mühlenbach.
The most important gate facing the Rhine was the Mars Gate (Marspforte), which was demolished in 1545 and is remembered in the street name Obenmarspforten and an inscription on the house located at Marsplatz 3-5. The name of the gate derives from its medieval name 'Markttor' (Market Gate). At Kurt-Hackenberg-Platz an underground visitors-centre will soon be opened, in which a 12-metre-long section with the remains of the harbour gate and a sewer can be seen.