The Glacis
Before the redevelopment of Vienna from around 1850, the city was surrounded by an unbuilt area outside the city wall – the Glacis. It originally served defensive purposes.
The first photo shows the view of the Josefstadt with the Glacis, the Military Geographical Institute and the Piarist Church behind it can be seen clearly.
Blick Richtung der heutigen Bezirke 8 und 9 
Die Ringstrasse im Bau (beim Heldentor) 
(“graues Haus”, Landesgericht Wien)
Image sources : ÖNB Digital, WIEN MUSEUM Onlinesammlung
