The detailed southern tour of Gamla stan, the old town of Stockholm

The south of the old town Gamla stan!
 Many guides take city tours through the entire old town of Stockholm, but no, that's not possible, a lot of interesting things have to be left out! That's why I'm offering a southern tour here, just the south of the Gamla stan. What do you know about land elevation, crooked windows, singing troubadours, iron, the narrowest street in Stockholm and the conspiracy theories in it, the Germans, the Finns, ... and much more.
 Come along and convince yourself!
 PS: Part 2 is the northern part of the old town!