Canals in Leiden: the Rhine with the Apothekersdijk (Apothecaries' Dike) on the left and the Boommarkt (Tree Market) on the right

Up to the 1960s Leiden was based on transport by water, that meant that every time a ship passed through Leiden, road transport had to wait. In the 1960s the City Council decided to give priority to the road, so they filled up several canals and diverted the ships around Leiden. Luckily they didn't fill up all the canals.