[koyote]

I've done this wherever I lived.

In a large city, you can often just walk in one direction, (or take transport in one direction), find yourself in a new neighbourhood and discover loads of interesting things (culture, food, shops, parks, ...).

In London there are hundreds of walks/hikes around and beyond the green belt, all within an hour train from central London.

I do agree that there are some places where this is more challenging.