 The first three were connected through Milan via the "Fossa Interna", also known as the Inner Ring.The urban section of the Naviglio Martesana was covered over at the beginning of the 1930s, together with the entire Inner Ring, thus sounding the death knell for the north-eastern canals.Commercial carrying continued on the Naviglio Grande, but the decline was steady and by the 1960s a project of a fluvial port to reach the Po River and consequentially the Adriatic Sea through the canals was shelved for good.