I'm currently living in Oslo, Norway.

I think one of the great things with this city is the closeness to nature. Just some few kilometres from the central station, it's possible to sit on a picnique-bench by the seaside with great views and not a single car or car road to be seen (Hovedøya, easily available by public ferries) - and there are quite many islands around that belong to the commons.

There is also the forest. The municipality consists of lot more forest than city - the geographical midpoint of Oslo is in the middle of the forest, north of the city itself.

Common areas typically gets eaten up due to the imbalance - if some politician permits building or privatization of the common land, it's pretty much an irreversible act. At the other hand, if someone wants to build and their application is rejected, it's easy to apply again. Bit by bit, common land may disappear as different politicians take office. Now, they've done some political handcraft here - they've managed to protect the forests in Oslo and the surrounding areas by national law. Hence, it's not sufficient that some local politician thinks it's OK to make forests into residental areas, it's needed to lift it up to the national level - the border between forest and city has become a sacred line that is not to be crossed (not with construction machinery, at least). The forest is easily accessible by metro, bus and train. Like, some 25 minutes by train from the central station, and some 15 minutes walk, and one will have magnificent view - forest, forest, forest and nothing but forest as far as one can see.

(I've upvoted my own comment, I think that's perfectly OK since I'm giving even more upvotes to many of the other comments here)