Trostburg castle was probably built in the 12th century, though nothing is known of its early history. At some point in the 12th or early 13th century a junior line moved a short distance away and built Liebegg Castle near Gränichen. On 28 May 1241 Burkhart I of Trostberg and his relative Ludwig of Liebegg appear in a document as witnesses and unfree knights in service to the Counts of Kyburg. Eventually they passed from Kyburg service to Habsburg service. In 1317 a knight named Rudolf von Trostberg was the Habsburg vogt at Kyburg Castle.
Around the mid-14th century the Trostburg line died out. The castle and surrounding estates were inherited by the Lords of Rinach. In 1415 the city-state of Bern conquered the Aargau from the Habsburgs. The owner of the castle, Hans Rudolf von Rinach, kept his castle and lands, but was forced to accept Bernese authority and grant them a preeminent right to buy it. In 1486 the Schultheiss and council of Bern decided to sell Trostburg along with its lands and serfs to Hans von Hallwil, the victor of the Battle of Murten.
Under the Hallwil family, the castle was fortified and expanded with a chapel and residence hall (known as the Hallwil House) added on the northwest side of the site. It remained with the Hallwil family for 130 years. In 1616 Hugo von Hallwil moved to Bohemia and tried to sell the castle to the city of Brugg. Apparently fearing that Brugg was expanding its influence, the city of Bern quickly bought the castle and then sold it to a cooperative of wealthy Bernese citizens. Bern retained the rights to high justice and some income, which they transferred to Lenzburg Castle. Over the following century the castle fell into ruin except for the Hallwil House. In 1754 it was described as looking like a peasant's hovel.
In the 19th century found the castle converted into a music box factory. In the early 20th century it was partly rebuilt by a German butcher, but World War I prevented project completion. A large part of the western curtain wall collapsed in 1922. In 1933 it was acquired by another private owner who used the castle as his private residence. An archeological project in 1999 explored the history of the castle and also repaired and strengthened many of the walls.
Castle site
The castle is located on the same line of hills on which Liebegg Castle stands and the remaining castle walls wrap around the local hill top. The bergfried is a square 6.6 meters on each side and about 7 meters tall. The hill falls away from the tower toward the north, with a courtyard south and west. West and north of the courtyard the ground slopes down toward the Hallwil House. The residence building is four stories tall with massive walls that are between 1–1.7 m thick.
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Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).