The old town (Gamla Stan) in Stockholm is a place mostly crowded with vistors but if you get up a little earlier you can have the streets almost for yourself, which make taking pictures a bit easier :-)
Södermalm (the southern city) in Stockholm was earlier a working class part of the town, nowadays it's full of "culture workers" and hipsters ;-) ( And a lot of new bars, restaurants and pubs). I grew up here in the 60's & 70's and almost can't regognize the place today.
The Metro/underground (Tunnelbana) in Stockholm is famous for the design of many of the newer stations, here some pictures from the station "Kungsträdgården". More about this you can find in this article from the Guardian