I had the same reaction when I saw this article on CNN a week ago. A little more exciting than "lost drain pipe discovered under Utah couples' home", but not by a whole lot!

At least the title was descriptive and not "You won't believe what was discovered under Sforza Castle".

The tunnels they found are definitely plural though, only the connection to the sketches seems a bit tenuous.

> It features a well-known underground passageway that runs along the perimeter of the castle’s moat and is accessible to tourists. But to the researchers’ surprise, their survey revealed a second secret tunnel that experts had only hypothesized about for years.

The second tunnel runs parallel to the first one, about 1 meter (3 feet) beneath the surface. [...]

The researchers also uncovered other tunnels [...] including one that heads in the direction of the Basilica of Santa Maria delle Grazie, the resting place of the wife of Duke Ludovico Sforza.

From the title I wasn't sure if they were even found