The Gate can be visited
Town Fortification Nürnberg-Spittlertor

Located in the southwest of Nuremberg, the Spittlertor is one of the four large round towers of the city fortification system and shapes the cityscape. It is a component of Nuremberg's historic city wall.
History+
As early as 1377, the Spittlertor was documented as part of Nuremberg's last city wall. It replaced the older gate tower, the White Tower. The gate served as an exit point towards Schwabach, Rothenburg ob der Tauber, and Donauwörth. In 1557, a reconstruction was carried out by Jörg Unger, resulting in the round tower still standing today and the construction of a new gate.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:N%C3%BCrnberg_Spittlertorturm_und_%C3%A4u%C3%9Feres_Tor_des_Waffenhofs.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 49.4484, 11.0669