The center of the Nieuwmarkt is the imposing weigh house. Built in 1488 as the Sint Antoniespoort: an important city gate that also served as a defensive stronghold. Due to an urban expansion in the late 16th century, the building was no longer situated on the outside of the city and lost its function as a city gate. In 1614, the part of the Kloveniersburgwal around the gate was filled in to create a new market square (hence the name Nieuwmarkt). A part of the gate disappeared underground. However, you can still sail underneath it by boat. The square was also known due to corporal punishment and executions. Nowadays there is a market with organic products every Saturday.

When the city gate was no longer a city gate, it was converted into a weigh house: roofs were made above the doors, under which scales were placed. This was not only for weigh goods for daily use, but also anchors and artillery from the nearby shipyards were weighted.

Some guilds were housed on the top floor of the weigh house. Until 1869, the Surgeons' Guild used the top floor, the Theatrum Anatomicum, as a lecture hall. Here, corpses of criminals were dissected during anatomy classes in winter. In 1632 Rembrandt painted here ‘De anatomische les van dr. Nicolaes Tulp’ (The anatomy lesson of Dr. Nicolaes Tulp). Nowadays Restaurant-Café In de Waag is located in this historic building on the Nieuwmarkt. The beautiful terrace and historic interior make it a perfect place for a drink, lunch or dinner.