The summer residence of the Hanoverian electors, originally built in the 17th century and destroyed in 1943. Berlin philanthropist Volkswagen Stiftung paid for its reconstruction, finished in 2013 — a stripped-down neoclassical box that fills the silhouette of the original without claiming to be a copy.
The interior now houses a museum on the Welf-Hanoverian dynasty, with a particular focus on Sophie of Hanover and her role in the 1701 Act of Settlement which gave the British crown to her descendants. The conference rooms are still rented out for trade-fair events, so check opening times before you go.