Luxembourg comprises only 2,585 square km (999 square mi). Starting in AD 963, when Charlemagne's descendant Sigefroid began to build his castle atop the promontory of the Bock, the duchy encased itself in layer upon layer of fortifications until by the mid-19th century its very impregnability was considered a threat.
The Castle of Luxembourg was ultimately dismantled in the name of peace, its neutrality "guaranteed" by the 1867 Treaty of London. But the Grand Duchy was to be invaded twice again, in 1914 and 1940. Its experiences during World War II convinced Luxembourg of the necessity to cooperate with all its neighbors to avoid conflicts. The entire country now flaunts new wealth, new political muscle, and the highest per capita income in Europe.