The County of Luxembourg was a State of the Holy Roman Empire. It arose from medieval Lucilinburhuc Castle in the present-day City of Luxembourg, purchased by Siegfried, Count of the Ardennes in 963. His descendants of the Ardennes–Luxembourg dynasty began to call themselves Counts of Luxembourg from the 11th century onwards. The House of Luxembourg, a cadet branch of the Dukes of Limburg, became one of the most important political forces of the 14th century, contending with the House of Habsburg for supremacy in the Holy Roman Empire.

The Bock is a promontory in the north-eastern corner of Luxembourg City's old historical district. Offering a natural fortification, its rocky cliffs tower above the River Alzette, which surrounds it on three sides. It was here that Count Siegfried built his Castle of Lucilinburhuc in 963, providing a basis for the development of the town that became Luxembourg. Over the centuries, the Bock and the surrounding defenses were reinforced, attacked, and rebuilt time and time again as the armies of the Burgundians, Habsburgs, Spaniards, Prussians, and French vied for victory over one of Europe's most strategic strongholds, the Fortress of Luxembourg. Warring did not stop until the Treaty of London was signed in 1867, calling for the demolition of the fortifications. Ruins of the old castle and the vast underground system of passages and galleries known as the casemates continue to be a major tourist attraction.