The Roman Castle can be visited
Roman Castle Unterböbingen

The Roman fort of Unterböbingen, a former Roman military installation, is located in the eastern part of Böbingen an der Rems in the Ostalbkreis district, Baden-Württemberg. It was built on an elevated spur on the south bank of the Rems to secure the nearby Rhaetian Limes, which is now a UNESCO World Heritage site. The garrison once monitored approximately 20 Limes towers along a 15-kilometer stretch.
History+
Initial excavations in 1885 and 1886 by Eduard von Kallée identified Unterböbingen as a fort site. Further investigations commissioned by the Imperial Limes Commission by Major Heinrich Steimle in 1892 secured important findings. However, between 1930 and 1935, large parts of the complex, including the Praetentura and a multi-purpose hall, were destroyed by quarrying.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 48.8189, 9.9247