The River Waal's floodplain landscape is characterised by its curving dykes which shield numerous towns and villages of which at times only the church steeples are visible. Besides the grazing cattle on the floodplain there are also traditional brick-stone factories and shipyards. Amsterdam is reached via the 71 km long canal that links the port of Amsterdam with the River Waal at Tiel. The canal is not only Amsterdam's main waterway linking its port to other ports along the Rhine but it is also foremost in the drainage of the surrounding low lying countryside. This typical Dutch scenery with its green polders, windmills, forts and bicycle paths is known as the Dutch Green Heart, a legacy of the clever Dutch water defence line now a UNESCO World Heritage Site.