Unlike most Old Holland cities, Leiden does not have a central market square. Over the centuries, the water of the Rhine was a main artery for Leiden. Goods arrived in the city on flat barges. The cargo was then unloaded onto the quayside ready for sale. The transported goods were weighed in the Waag, or Weigh House. The weights were calibrated officially so buyers could be confident that they were not being swindled.

The present building dates from 1657 and was designed by one of the most eminent architects of the time, Pieter Post. The crane that stood in front of the building, on the quayside, was leased by the city. The crane operator assisted anyone who needed help with unloading their cargo – for a fee, of course.