From Utrecht, take a train to Rotterdam, the modern Dutch city. I would suggest visiting the UNESCO Heritage Site Kinderdijk first and then exploring Rotterdam later in the day. Take a tram from Rotterdam Central Station to Erasmusbrug. From there you will find waterbuses to Kinderdijk. The mill complex in Kinderdijk is quite a unique sight. Netherlands is partly under the sea water. It is said that if the Dutch let the nature run its course, then most of Netherlands would be under water today. These mills with pumps combined with the dikes at the sea dries a big part of the land so people can live there. Water plays a very important part in the Dutch life and they have since long found out measures to smartly deal with the surrounding water using wind and steam energy to keep the Netherlands above water. I really feel Kinderdijk is a must visit destination in Netherlands.