Mariembourg
... that although considered impenetrable when built, the fortress town of Mariembourg was taken by French troops after only three days of siege?
... that although considered impenetrable when built, the fortress town of <b id="mwBBY"><a href="./Mariembourg" id="mwBBc" rel="mw:WikiLink" title="Mariembourg">Mariembourg</a></b> <i id="mwBBg">(pictured)</i> was taken by French troops after only three days of siege?