Stockholm is a city of surprises: outdoorsy despite the cold climate; chilled despite being the capital; walkable even though it's spread over multiple islands; expensive but not nearly as pricey as other Nordic countries (Norway I am looking at you).
Stockholm City Centre (Innerstaden) is made up of seven areas: Norrmalm (the business district), Gamla Stan (old town, very touristy), Östermalm, Kungsholmen (both quite residential), Södermalm (cool bars and cafes), Djurgården (museums) and Vasastan (residential - bit posh perhaps? - with nice cafes and restaurants). Each area feels very different from the other but it would be perfectly possible to spend an entire weekend just on Södermalm. It's where all the main attractions are.
I visited Stockholm in the summer so I could avoid the risk of sub-zero temperatures but didn't expect it to be so gorgeously warm! Honestly, it was one of the best summer cities I have ever visited. So clean and lush, with great al fresco dining, parks and places to swim. I can't wait to go back!