Leuvehaven is a really nice and impressive old type of harbour in the middle of the city, I can only imagine how nice it must be to live there and enjoy the gorgeous view of the harbour every day! When you are coming from, for instance, the busy Witte de Withstraat you cannot miss the cranes that start appearing in front of you while you approach the harbour. The sight is especially impressive and romantic at night, when the lights that decorate the cranes and boats are lit.
A hundred years ago Leuvehaven was in full use as the place where the breweries were and where fish was traded. This stopped during the war, when most of the surrounding buildings were destroyed. Now the harbour is just a nice scenic place to walk through. You can grab a (old-fashioned) watertaxi here, or if you are looking for a nice place to eat or drink you can walk a bit further towards Vessel 11, a great place for some British cuisine, and a nice glass of beer.