From SciTechDaily: Underneath an Ancient Castle: Researchers Discover Secret Passages Linked to Lenonardo Da Vinci.
New research uncovered hidden passages under Sforza Castle, potentially confirming legends linked to Leonardo da Vinci’s designs.
As part of a PhD thesis, the Politecnico di Milano conducted an advanced technological survey in collaboration with the Sforza Castle, with technical support from Codevintec.
That sounds like a very fun PhD thesis.