Walking from Globen (the sun) to Naturhistoriska (the earth) could be made into a quite nice 10 km walk, with possible detours to see much of the old worker's t

Walking from Globen (the sun) to Naturhistoriska (the earth) could be made into a quite nice 10 km walk, with possible detours to see much of the old worker's town of Södermalm, the old town, the city center around Klara/Norrmalm, the urban residential area Sibirien, the university and finally ending up at the science museum Naturhistoriska. The Stockholm novels by Per Anders Fogelström starting with "City of My Dreams" largely plays out across that walk, if you're interested in the 19th/20th century evolution of the city and its working class. The metro's art project is also pretty cool if you take the subway when you're in Stockholm, with unique artwork at each station (spanning from a few pieces almost hidden away next to the ad billboards to the whole station decorated to an elaborate theme).