den Haag

location: 

about 5 miles north of Delft. The Vliet canal from Delft to Leiden turns northeast at Voorburg. There, the Haagvliet or Trekvliet branches off north another two miles to the Binnenhof (inner court) where parliament meets.

in English, the Hague. While Amsterdam is the current capital of the Netherlands, the Hague is where the royal family lives, parliament meets, other countries have their embassies, etc. In Leeuwenhoek's time, it was just as important, although Amsterdam was clearly the financial center.