Heidegg Castle is, according to the latest scientific research, the oldest residential building in the canton of Lucerne. It was built by the Lords of Heidegg, who constructed a stone house high above Lake Baldegg in the late 12th century, which was soon replaced by a residential tower. This richly illustrated book presents, for the first time, the construction and ownership history of the complex up to 1700, when the lordship passed to the city of Lucerne. Since then, the castle has hardly changed architecturally. The individual construction phases are clearly presented and placed within the context of regional and architectural history. The transformation from the high medieval stone house to the representative residential tower and then to the early modern country estate, which can also be observed in other castle complexes, is clearly evident. Additionally, a historical introduction outlines the development of the Lords of Heidegg. The Heidegg family can primarily be characterized as a regionally rooted lineage. Early on, they expanded their influence over the Seetal through marriage alliances. Unlike other noble families, however, they did not pursue careers among the Counts of Habsburg, nor did they move to a confederate city. Instead, they experienced a surprising new flourishing in the 15th and 16th centuries along the High Rhine as senior officials of the Dukes of Habsburg-Austria. Meanwhile, the ancestral castle became a country estate for Lucerne patricians.