The exact date of Altenburg Castle construction is unknown, however the traditional date given is during the reign of Valentinian I or around 370. The discovery of several small coin hoards near the ruins may indicate a construction date as early as the beginning of the 4th century AD.
The castle was built on a point above the Aar river as part of the Limes Germanicus to protect an easily fordable stretch of the river. The walls were 3–5 m thick and protected by six or eight half-round towers. Nothing is known about the number, location or purposes of the interior buildings.
The Schlössli was built in the ruins of the Roman castle during the late 10th century, probably for an ancestor of the famous Habsburg family. It remained the seat of that family until the construction of Habsburg Castlein the 11th century. After that time it became the seat of Habsburg bailiffs or knights. In 1397 the castle, village and the rest of the Habsburg Eigenamt were gifted to Königsfelden Monastery in Windisch.
On 16 November 1414, Emperor Sigismund called the Council of Constance to settle the Western Schism between the three popes (Benedict XIII, Gregory XII, and John XXIII), all of whom claimed legitimacy. Frederick IV of Habsburg sided with John XXIII. When John XXIII was declared an antipope, he fled the city with Frederick's help. The emperor then declared the Habsburg lands forfeited and ordered the neighboring countries to conquer those lands for the emperor. The city-state of Bern had already pledged their support of the emperor against the Habsburgs in 1414, and so they were ready to invade. Following a series of Confederation victories, in 1415 much of the Eigenamt including Altenburg was in Bernese hands. After Bern assumed control, the monastery retained most of their rights to the land and castles.
In 1528 Bern adopted the new faith of the Protestant Reformation and quickly seized and secularized all of the lands of the religious houses. Under Bernese rule, the castle remained a minor manor house tucked away in the country. During the 16th century a late Gothictower house topped with crow-stepped gables was added. In 1941 it was converted into a youth hostel, which it remains today.References:
The famous Italian Medici family have given two queens to France: Catherine, the spouse of Henry II, and Marie, widow of Henry IV, who built the current Luxembourg palace. Maria di Medici had never been happy at the Louvre, still semi-medieval, where the fickle king, did not hesitate to receive his mistresses. The death of Henry IV, assassinated in 1610, left the way open for Marie's project. When she became regent, she was able to give special attention to the construction of an imposing modern residence that would be reminiscent of the Palazzo Pitti and the Boboli Gardens in Florence, where she grew up. The development of the 25-hectare park, which was to serve as a jewel-case for the palace, began immediately.
The architect, Salomon de Brosse, began the work in 1615. Only 16 years later was the palace was completed. Palace of Luxembourg affords a transition between the Renaissance and the Classical period.
In 1750, the Director of the King's Buildings installed in the wing the first public art-gallery in France, in which French and foreign canvases of the royal collections are shown. The Count of Provence and future Louis XVIII, who was living in Petit Luxembourg, had this gallery closed in 1780: leaving to emigrate, he fled from the palace in June 1791.
During the French Revolution the palace was first abandoned and then moved as a national prison. After that it was the seat of the French Directory, and in 1799, the home of the Sénat conservateur and the first residence of Napoleon Bonaparte, as First Consul of the French Republic. The old apartments of Maria di Medici were altered. The floor, which the 80 senators only occupied in 1804, was built in the middle of the present Conference Hall.
Beginning in 1835 the architect Alphonse de Gisors added a new garden wing parallel to the old corps de logis, replicating the look of the original 17th-century facade so precisely that it is difficult to distinguish at first glance the old from the new. The new senate chamber was located in what would have been the courtyard area in-between.
The new wing included a library (bibliothèque) with a cycle of paintings (1845–1847) by Eugène Delacroix. In the 1850s, at the request of Emperor Napoleon III, Gisors created the highly decorated Salle des Conférences, which influenced the nature of subsequent official interiors of the Second Empire, including those of the Palais Garnier.
During the German occupation of Paris (1940–1944), Hermann Göring took over the palace as the headquarters of the Luftwaffe in France, taking for himself a sumptuous suite of rooms to accommodate his visits to the French capital. Since 1958 the Luxembourg palace has been the seat of the French Senate of the Fifth Republic.