Just off Vienna's happy-go-lucky Mariahilfer Strasse, I came upon a mighty WWII flak tower built in 1944, which still functions as a shelter for the Austrian government in times of crisis. There are several such WWII towers in Berlin, Hamburg, and Vienna -- all built after Hitler realized he might be defending his empire on his own turf.
This is Day 53 of my 100 Days in Europe series. As I research my guidebooks and make new TV shows, I'm reporting on my experiences and lessons learned in Vienna, the Alps, the Low Countries, England, and beyond. Find more on my travel blog.
(This post originally appeared at blog.ricksteves.com/wwii-flak-tower-vienna.)