Secret Tunnel

This is the entrance of the Regents Canal to the Islington Tunnel, which is almost 1Km long! When it was first opened in 1820, bargees used to have to navigate the tunnel by lying on their backs on their barges and pushing the barge along with their feet. Read about it here. And the "secret" bit over the last few days is because I doubt many Londoners know of their existence or significance. Save my educated and informed visitors, of course.