The canal you just walked next to, Kloveniersburgwal, was a location of Amsterdam's walls in the past. You've already seen de Waag building that used to be a city gate. However, here is a location of another defensive tower - Doelen. Dutch cities were sometimes in war with each other and that was often the case with Amsterdam and Utrecht. That's why they would built this kind of defensive towers to protect themselves. On a building in front of you, there is a white panel with an image of the old Doelen Tower. Since, at one point Rembrandt lived just around the corner of it, we also have a drawing of the tower made by him. You can find it at the Rembrandt House Museum today.