Södermalm is the place to be in Stockholm, especially this section of it. Close enough to Old Town (Gamla stan) to walk if you want and different enough to enjoy the differences. There are so many great little places all around Jonas' flat and it's easy to get to the ferry, the T-bana and commuter rail from his place. Jonas went above and beyond coming all the down to the T-station to walk me back to his place when I was really lost! He is a great host.