The so-called “Conca di Viarenna” is what remains today of one of the 5 canal locks used to navigate through Milan from the Darsena and the Naviglio Martesana along a section called “Fossa Interna”. The latter was closed to navigation and covered over in the 30s. The lock was built in 1439 by Filippo Maria Visconti. At one end of the Conca di Viarenna, a 1497 plaque displaying the coats of arms of the House of Sforza commemorates the duke Ludovico il Moro and his wife Beatrice d’Este. A Latin inscription can also be read, granting a toll free passage to all boats from Lake Maggiore carrying marble for the building of the Cathedral.