We don't usually believe in curses, but we might make an exception for Neuruppin Mansion, which is in Germany. Just building it bankrupted its first owner. Ludwig von Diebitsch went badly over budget on his mansion project, and was penniless by the time work was completed in 1877. He never lived a single day inside it.
The next owners tried to fund the upkeep of the mansion by growing sugar beet on the grounds, but the low-quality soil couldn't support the crops, and so they lost their money too. It was abandoned after World War Two.