Luxembourg was famous for its fortifications and was named the Gibraltar of the north, as it was suggested to be impregnable. In the center between rivalling countries it was always a sort of strategic post. During the history it was occupied several times by Spain, France, Austria and Prussia. Each country tried to fortify the Capital. Famous master builders, like Sébastien Le Prestre de Vauban, Isaac von Traybach, and Freiherr von Thüngen created huge walls, forts and towers, each one on the height of its time.
Finally Luxembourg became independent as a Grand Duchy in personal union with the Netherlands. With the First Treaty of London in 1839, its independence was reaffirmed. The Luxembourg Crisis nearly led to war between Prussia and France, but the Second Treaty of London again affirmed Luxembourg's independence and neutrality in 1867. However, this treaty also resulted in the the destruction of the Confederate fortress. Most of the fortifications of Luxembourg were razed, only basements, casemates and a few walls remained. The city of today is built on this basements, and from the surrounding valleys the remaining basements still give the impression of a fortified city.