Riddarfjärden
Riddarfjärden (, "The Knight Firth") is the easternmost bay of Lake Mälaren in central Stockholm. Stockholm was founded in 1252 on an island in the stream where Lake Mälaren (from the west) drains into the Baltic Sea (to the east); today the island is called Stadsholmen and constitutes Stockholm's Old Town.
Stockholm during the Swedish Empire
On "Malmarna", the surrounding ridges, the first suburb to catch the focus of Oxenstierna was the western part of Norrmalm. A city plan for the district, most likely developed by Anders Torstensson in early 1637, feature several still preserved structures, including "Stoore Konnungz gatun" ("Large King's Street", today's Drottninggatan) and "Mönstre Platz" ("??", today's Hötorget). 
A second devastating fire in 1640 on the eastern part of Norrmalm provided the excuse for a city plan for that district, and at the same time the rural area east of Norrmalm ("Ladugårdslandet", today's Östermalm) was donated to the city. Soon Torstensson presented a unified plan for all three northern suburbs, long after his death realized with only minor changes. One of the problems he failed to deal with was the huge ridge Brunkebergsåsen separating the two parts of Norrmalm, and misfits between the non-aligned streets on either side can be seen on modern maps of the city.