The Suouth part  of Vasterlanggatan street is curved and ended on a small square Järntorget (Iron sqare, map). The square was formed in the early 14th century, and originally bore the name Korntorget (grain size), as were brought here for sale wheat and corn. Name Jarntorget first mentioned in 1489, both names are used in parallel to 1513, while the trade of iron did not supplant agricultural products. Iron smelted from the rich ore deposits of lake mälaren, has long been the main export commodity of Sweden and was appreciated throughout Europe. Trade has brought great income into the city Treasury, as brought from smelters in the metal prior to loading on ships definitely were weighed at public scales, and the weight was taken duty. Major urban scales appeared on the square in the middle of the 14th century. In addition gelasa for export was copper, and various metal products. Surrounding the house was inhabited by German merchants in the 15th century they were ousted by the Dutch, the French and the British.

In the Middle ages the area was approximately twice more than today. In the early 17th century in the surrounding houses there were many taverns, and in 1662 the city's official scales were relocated to södermalm. The area begin to populate wealthy people who demolished medieval hovels and build up the area with new and beautiful buildings. Construction is encouraged by the king, wishing to give the city a respectable appearance. On the area also is building the world's first state-owned Bank - the National Bank of Sweden, built in 1680. In the 18th and 19th century, the area was used as a green market.

In the middle of the square remained a well with a hand pump - another example of cast-iron architecture. As you can see, to the problem of water supply, the city authorities took seriously at all times - the well can be seen on each square of Gamla Stan.

Judging by the wall thickness of the metal in Sweden are not saved.

Near the Iron square, from Vasterlanggatan begins the  Martin Trotzig, the narrowest street in Stockholm.