The Canal entrance is quite discreet, opening through a tunnel. The Canal was created during the "Restauration" period, from 1821 to 1825. It has 4.5 km. The entrance is crossed by several viaducts for highways and metro. The Canal Saint Martin connects the Seine river in Paris to the Canals l'Ourq and Saint Denis and then goes into the Seine again. This shortcut allows boats a 12 km saving.After crossing through the tunel, the Canal opens to the Arsenal marina. This port is the only real marina in Paris. It can accomodate more than 200 boats. The covered part (from Bastille) is now the Richard Lenoir Boulevard. This was done in the middle of XIXth century to allow the reunification of the outside districts to the city.The Canal crosses the "10ème arrondissement". Here starts the real open-skies Canal St-Martin. And the Canal goes further, another time underground, just to pass under Stalingrad crossroads. After crossing the roads we enter the "XIXème arrondissement". There we find the huge La Villette pond and a funny circular structure called Rotonde de La Villette. It had been once a special market place. The end of the La Villette pond coincide with the connection with the Ourcq Canal. There, a peculiar drawbridge serves as a barrier.