Ahlden House () is a stately home at Ahlden on the Lüneburg Heath in Lower Saxony, Germany. It was built in 1549, originally as a water castle on the river Aller, which has since changed its course. Nowadays the three-winged mansion is a private residence and is used as an arts auction house. It is principally known as the place of imprisonment of Sophia Dorothea of Celle, otherwise Sophie Dorothea of Brunswick-Lüneburg, wife of George I of Great Britain and the mother of George II of Great Britain. Location Opposite the mansion, in a depression on the other bank of the river, was the old castle of Bunkenburg which lies today in ruins. It is believed to have been built in the 13th century. It was established opposite the village of Ahlden on the banks of the Aller. In 1618, during a flood, the Aller shifted its channel towards the east and, as the result of an embankment downstream, the waters of the Leine then flowed past Ahlden in the bed of the former Aller. Since 1648 the course of the "Old Leine" has become a partly dried oxbow lake. The present house was built in the 16th century on the river bank by Ahlden opposite the Bunkenburg. Today it is located on the old branch of the Aller, which was the one that channeled the waters of the Leine in 1618 and has since been called the "Old Leine". Construction Much of the house is of timber-framed construction; only the ground floor of the west wing being built of brick. The building today consists of three, two-storey wings in the shape of a horseshoe, which were built in 1549. In earlier centuries the site was, for a time, almost entirely enclosed and had an interior courtyard. The individual wings of the building were not only used for residential rooms, but as for stables and coach houses (Remisen). The west wing is the main building of the mansion, which Duke Christian the Elder of Brunswick-Lüneburg had built by his seneschal (Drost), Johann Behr, in 1613. On the entranceway leading to the inner courtyard the wall recesses for the drawbridge can still be seen. During the construction of the wing in 1613 there was a serious accident when a roof joist dislodged and seriously injured 14 workers. The south wing, a timber-framed structure with brick infill, is the oldest part of