Kasteel van Hoensbroek - Hoensbroek,Netherlands

There is a blue lady wandering around in the castle of Hoensbroek. She is said to have been a inhabitant of the castle, whose two children died at an early age. They were supposedly buried inside the castle walls while the blue lady wasn't informed. Now she searches for them at night. Many people that have worked at the castle at night claim to have seen the blue lady. One security guard swears that he heard chairs being moved in a room he had just visited and when he went back to take a look, he indeed found the chairs in a different position than he had seen them just a moment before. The walls of the castle sound solid when knocking on them, except for one wall which sounds hollow. It has never been investigated, but could this be the place where the two children are buried?