Once only indicated through a sketch by Leonardo da Vinci from around 1495, concealed passageways have been discovered ...

A series of underground passages have been found under Sforza Castle in Milan by experts at the city's Polytechnic University ...

A series of underground tunnels first sketched by da Vinci in 1495 have finally been found below a castle in Milan, Italy.

But it was during the medieval era when the tunnels became essential pathways ... With medieval architecture comes impeccable taste in art, and the Museo del Colle del Duomo is a good introduction.