In 2009, archaeologists from Frankfurt's Office for the Preservation of Historical Monuments were able to uncover a section of the city's fortifications, which the fortress builder Dilich had built starting in 1628. In the process, they also uncovered a subterranean gallery, which apparently does not exist in any other part of Frankfurt's baroque city wall. With a walkable length of over 40 m and a clear height of 4 m, this defensive structure represents an imposing and high-ranking cultural monument.
Source of text and further information on this event: https://www.archaeologisches-museum-frankfurt.de/pdf/Januar_Juni_2019.pdf
